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The UK Multinational Top-up Tax and Domestic Top-up Tax under Finance (No. 2) Act 2023 were amended again for accounting periods beginning on or after 31 December 2025. For a calendar-year group, the first return and first payment both fall on 30 June 2026, the floor below which no filing date can drop.
Market commentary treats the UK Multinational Top-up Tax and Domestic Top-up Tax as a new tax bolted onto Corporation Tax. The framing misleads. The two charges are a parallel computation that runs alongside the Corporation Tax return on a separate calendar, a separate registration, and a separate liability, and produces a charge only where a territory's effective tax rate falls below 15%. For a UK group at or above the EUR 750 million revenue threshold, the Corporation Tax return continues to be filed as before. What is added is a second computation that takes the same financial data, re-expresses it under the Global Anti-Base Erosion (GloBE) rules, tests the jurisdictional effective tax rate against 15%, and charges the difference where the rate falls short.
The distinction determines the work. Treated as a new tax, the regime looks like a rate increase to be modelled. Treated as a parallel computation, it is a reporting and evidence architecture that has to be built once and run every year, whether or not a top-up charge actually arises. The point that catches groups in 2026 is that the obligation to register and to file exists even where the top-up tax is nil. A UK group whose every territory already pays above 15% still registers and still files. The liability may be zero; the compliance is not.
This is the first filing year. Multinational Top-up Tax and Domestic Top-up Tax took effect for accounting periods beginning on or after 31 December 2023. For a calendar-year group, the first in-scope period is the year beginning 1 January 2024, and the first return is due 30 June 2026 under the rule that no filing date can fall before that floor (HMRC manual MTT53010). The regime was amended by Finance Act 2024 and Finance Act 2025, and amended again by the 2025 measure that takes effect for accounting periods beginning on or after 31 December 2025. The group registering and filing for the first time in 2026 is doing so under a statute revised three times since enactment.
This article walks the statutory frame in Part 3 and Part 4 of Finance (No. 2) Act 2023, the substance of the 2025 amendments and their operative dates, the registration mechanic, the 15-month and 18-month filing windows and the 30 June 2026 floor, the split between the information return and the self-assessment return, the payment mechanic, the way the UAE QDMTT Safe Harbour discharges UK Multinational Top-up Tax on UAE income, the five recurring first-filing traps, and the sequencing with the UAE and Ireland legs of the corridor. The UK top-up tax is not the hardest computation a corridor group will run in 2026. It is the one that has to be filed first.
The UK gives effect to Pillar Two through two distinct charges, both contained in Finance (No. 2) Act 2023 and both administered through the single code in Schedule 14.
Multinational Top-up Tax (Part 3). Multinational Top-up Tax (MTT) is the UK's implementation of the Income Inclusion Rule (IIR), the primary GloBE charging mechanism. It gives the UK the right to charge a top-up tax on the low-taxed income of the foreign members of a group headed or part-owned in the UK. MTT has effect for accounting periods beginning on or after 31 December 2023 (HMRC manual MTT01010). The Undertaxed Profits Rule (UTPR), the GloBE backstop that allocates a top-up charge where no IIR has captured it, is implemented within Multinational Top-up Tax as a separate charging mechanism for accounting periods beginning on or after 31 December 2024. The UTPR was introduced by Finance Act 2025; its later start date is the single most important date distinction inside the UK regime, because it means the first MTT filing for a calendar-year group covers a period (FY2024) in which the IIR applied but the UTPR did not.
Domestic Top-up Tax (Part 4). Domestic Top-up Tax (DTT) is the UK's Qualified Domestic Minimum Top-up Tax (QDMTT). Under DTT, qualifying entities located in the UK with an aggregate effective tax rate below 15% are charged a top-up amount, so that the UK, rather than any other territory, collects the top-up on UK profits (HMRC manual MTT01200). DTT shares the implementation date of MTT and is calculated and administered in a largely similar way, with the Part 4 provisions replicating the Part 3 provisions with modifications. DTT is designed to be treated as a QDMTT by the OECD Inclusive Framework under section 265 of Finance (No. 2) Act 2023, so any DTT liability is fully offset against Pillar Two liabilities that might otherwise arise in other territories. The scope of DTT is wider than MTT in one respect: wholly domestic groups and single entities meeting the EUR 750 million threshold can fall within DTT even though they have no multinational footprint.
The threshold. Both charges apply to a group whose Ultimate Parent Entity has consolidated annual revenue of EUR 750 million or more in the consolidated financial statements in at least two of the four accounting periods immediately preceding the period in question. The threshold mirrors the OECD GloBE Model Rules and the UAE Domestic Minimum Top-up Tax threshold, which is what allows the corridor numbers to reconcile across jurisdictions. HMRC estimates approximately 4,250 multinational enterprises with global revenues above EUR 750 million are affected by the UK rules.
The single administrative code. Schedule 14 to Finance (No. 2) Act 2023 contains the administration for both charges: the filing member rules (Part 2), the information return (Part 4), the self-assessment return (Part 5), and payment (Part 10). A group in scope of both MTT and DTT registers once, files once, and pays through one mechanism, with the two charges computed within the same returns. The foreign-income charge (MTT) and the UK-income charge (DTT) are administered as one obligation even though they are two taxes.
The UK has revised the Pillar Two legislation in every Finance Act since enactment. The amendments matter for the first filing because the group filing in 2026 has to apply the version of the law that was in force for the period it is reporting, and the law for periods beginning on or after 31 December 2025 is not the law for periods beginning on or after 31 December 2023.
The legislative history. Multinational Top-up Tax and Domestic Top-up Tax were introduced in Finance (No. 2) Act 2023 for accounting periods beginning on or after 31 December 2023. Amendments were then made by Schedule 12 to Finance Act 2024 and Schedule 4 to Finance Act 2025. The UTPR part of Multinational Top-up Tax was introduced by Finance Act 2025 for accounting periods beginning on or after 31 December 2024. The 2025 measure is the next revision in that sequence.
Provenance of the 2025 measure. The 2025 amendments to Part 3 and Part 4 were published in draft on 21 July 2025, confirmed at the Budget of 26 November 2025, and carried in the Finance (No. 2) Bill 2024-26. The stated objective is narrow: to update UK legislation in line with the Administrative Guidance published by the OECD in January 2025, and to make amendments identified from stakeholder consultation or otherwise necessary to keep the UK rules consistent with the GloBE commentary and Administrative Guidance. HMRC scores the measure as nil for Exchequer impact and negligible for administrative cost, on the basis that it makes the legislation work as originally intended rather than changing the substantive charge.
Operative dates. Most provisions take effect for accounting periods beginning on or after 31 December 2025, with most also available, at the election of affected taxpayers, from an earlier date. The exception is the change to the treatment of pre-regime deferred tax assets, which takes effect for accounting periods ending on or after 21 July 2025. The split date is a drafting feature that a first-time filer needs to read carefully: the deferred tax asset change reaches back into periods that end after L-day 2025, which can include the very first period a calendar-year group is reporting.
The substance. The 2025 measure amends Parts 3 and 4 to give effect to a long list of technical changes. The ones most likely to touch a corridor group are:
None of these is a rate change. The substantive charge (15% on low-taxed income, computed jurisdiction by jurisdiction) is unchanged. What the 2025 amendments change is the precision of the computation and its alignment with the OECD guidance that other jurisdictions, including the UAE, are also adopting. The corridor consequence is that the UK and UAE computations move in step: the UAE adopted the OECD Commentary and Administrative Guidance through January 2025 by Ministerial Decision No. 88 of 2025, and the UK adopted the same January 2025 guidance through the 2025 amendments. The two regimes are calibrated to the same OECD baseline.
Registration is the first obligation, and it runs on a clock that is independent of the filing clock. A group can be late to register even while it is early to file.
Who registers. A single entity, the filing member, deals with all aspects of administration with HMRC for the group (HMRC manual MTT51010). By default the filing member is the group's Ultimate Parent Entity, even where the Ultimate Parent is located outside the UK (MTT51100). A group with an overseas parent may nominate a UK group member as the filing member instead, which is the common arrangement for a UK sub-group of a foreign-headed multinational. Agents and tax advisers cannot register on the group's behalf; the registration is made by the group itself through an organisation Government Gateway account.
When to register. The filing member must register with HMRC no later than 6 months after the last day of the accounting period in which the group first became a qualifying multinational group (HMRC manual MTT51400, paragraphs 6, 8 and 9 of Schedule 14). The trigger is the first day of the first qualifying period; the deadline is six months after that period ends. For a calendar-year group that first qualifies for the period ending 31 December 2024, registration is due by 30 June 2025. The registration deadline therefore falls a full year before the first return is due (30 June 2026), which is the point most often missed: the group that defers everything to the 2026 filing date has already breached the 2025 registration deadline.
What registration requires. The filing member supplies the name of the filing member, the name of the Ultimate Parent Entity if different, the first day of the first qualifying period (the trigger day), and the end date of that period. The registration tells HMRC whether the group has UK-only entities (DTT only) or UK and overseas entities (MTT as well as DTT). The group is obliged to register if it is a qualifying group and contains at least one UK-located member; a group with an overseas Ultimate Parent and UK members must still register. A single registration covers both Multinational Top-up Tax and Domestic Top-up Tax where both apply.
Changes after registration. If registration information changes, the filing member must notify HMRC by the later of 6 months after the change or, where the change is in the same period as the trigger day, the last day of that period. Replacing the filing member is done through the dedicated HMRC service. A group comprised entirely of excluded entities is not required to register.
The filing architecture sits in Schedule 14 and is the same for the information return, the self-assessment return, and the payment. Three numbers govern it.
Fifteen months as standard. A self-assessment return, or a valid below-threshold notification, must be submitted to HMRC within 15 months of the end of the accounting period (HMRC manual MTT53010, Part 5 Schedule 14). The information return or overseas return notification runs on the same 15-month clock (MTT52010, Part 4 Schedule 14). For a calendar-year group, a standard period ending 31 December produces a filing date of 31 March fifteen months later.
Eighteen months for the first period. A group has 18 months, not 15, to submit the return for the first accounting period it is subject to MTT. The three-month extension exists because the first cycle carries the one-off cost of building the GloBE computation, registering, and producing the information return for the first time. The extension is automatic on the facts; it applies to the first in-scope period and reverts to 15 months for every period after.
The 30 June 2026 floor. The filing date for a return cannot fall before 30 June 2026. Where the 15-month or 18-month calculation would produce an earlier date, the filing date is instead 30 June 2026 (HMRC manual MTT53010). This is the UK-specific floor that has no analogue in the UAE regime, and it is the single date that defines the first UK filing cycle. For a calendar-year group whose first in-scope period is FY2024 (1 January to 31 December 2024), the 18-month extension would give a date of 30 June 2026, which coincides with the floor. For a group whose period ended earlier, the 15-month or 18-month date might fall before 30 June 2026, in which case the floor moves it to 30 June 2026. No UK Pillar Two return is due before 30 June 2026, whatever the period-end.
The worked dates. For a calendar-year group:
The progression matters for the corridor calendar. The first UK filing (30 June 2026) and the first UAE DMTT filing (30 June 2027 for FY2025 calendar-year groups, under the UAE 18-month transitional window) do not coincide; the UK first filing runs a full year ahead of the UAE first filing, because the UK regime started a year earlier.
The first cycle is not one filing but a set of coordinated filings, and conflating them is a common first-year error.
The information return. The filing member must submit an information return to HMRC for each accounting period in which the group qualifies (HMRC manual MTT52010, Part 4 Schedule 14). The information return is the UK expression of the GloBE Information Return (GIR): the standardised, OECD-aligned data return that reports the group's GloBE Income, Covered Taxes, effective tax rate, top-up amounts, and safe harbour elections, for every territory in which the group operates, not only the UK.
The overseas return notification. Where the information return has already been submitted to another qualifying authority abroad, the filing member is not required to submit it again to HMRC and may instead send an overseas return notification (HMRC manual MTT52010). The notification states the jurisdiction to which the information return was submitted and the group member that submitted it. For the foreign authority to be a qualifying authority, its jurisdiction must be a signatory of the Multilateral Competent Authority Agreement on the Exchange of GloBE Information of January 2025; HMRC then obtains the return from that authority through automatic exchange of information. This is the mechanism that gives effect, on the UK side, to central GIR filing: a UK sub-group of a foreign-headed multinational that files the GIR in the parent jurisdiction discharges the UK information-return obligation by notification rather than by re-filing.
The self-assessment return. The filing member must submit a self-assessment return for each accounting period unless it has submitted a below-threshold notification (HMRC manual MTT53010, Part 5 Schedule 14). The self-assessment return constitutes the self-assessment of the group's total MTT liability and of the liability of each member of the group for the period. It is required from all registered groups, including groups with no MTT liability for the period and groups with no responsible members in the UK. The information return reports the data; the self-assessment return fixes the liability. They are two filings, not one, and the self-assessment return cannot be discharged by an overseas notification.
The below-threshold notification. A group that has registered but is no longer over the EUR 750 million threshold for a period can submit a below-threshold notification in place of a self-assessment return, which keeps the registration live without filing a full return for a period in which the group is out of scope.
Amendments. A self-assessment return may be amended by notice to HMRC any number of times within 12 months beginning with the filing date, regardless of when the return was actually submitted. The information return is amendable on the same 12-month basis. The amendment window is generous, but it runs from the filing date, not the submission date, so an early filer does not extend its amendment window by filing early.
Payment runs on the same calendar as filing, which simplifies the cash-flow planning but removes any gap between assessing the liability and settling it.
MTT and DTT liabilities must be paid in full within 15 months beginning with the day after the end of the accounting period, extended to 18 months for the first period for which the group is qualifying (HMRC manual MTT54100, paragraphs 32 to 33 of Schedule 14). The payment date aligns with the filing date for the self-assessment return and the information return. Because the dates are aligned, the 30 June 2026 floor applies to payment as well: where the filing date is moved to 30 June 2026 by the floor, the payment date is 30 June 2026 too.
There is no instalment regime for the top-up taxes and no payment-on-account mechanism of the kind that applies to large-company Corporation Tax. The full liability falls due on the single filing date. Late payment interest accrues from the day after the payment date at the rate set under section 178 of the Finance Act 1989. HMRC may issue a group payment notice where liabilities are not paid, and one group member may discharge another's liability under the Schedule 14 group payment rules, with a statutory right of recovery for the payer.
For a corridor group the practical reading is that the UK top-up tax has a single hard payment date per period, aligned to the return, with no smoothing. The cash position has to be modelled to that date, and for the first period that date is 30 June 2026.
The corridor crux of the UK regime is how it treats income that has already borne a top-up tax in another territory. The answer is the QDMTT Safe Harbour, and it is the mechanism that keeps UAE income out of the UK Multinational Top-up Tax charge.
The mechanism. A domestic minimum top-up tax that gives sufficiently similar outcomes to Pillar Two is treated, by agreement at OECD level, as a Qualified Domestic Minimum Top-up Tax (QDMTT). Where a QDMTT meets further criteria, it is accredited for the QDMTT Safe Harbour. Where a QDMTT is accredited, group members in the territory covered by that QDMTT may be treated, by election, as having no top-up amount or additional top-up amount for UK purposes (HMRC manual MTT15110). The election is made separately for standard members, joint venture groups, investment entities, and minority-owned members. The effect of the election is that the UK Multinational Top-up Tax does not compute or charge a top-up on the income of the members in that territory, because the territory's own QDMTT is accepted as having brought the rate to 15%.
The UAE position. The UAE Domestic Minimum Top-up Tax under Cabinet Decision No. 142 of 2024 achieved OECD Transitional Qualified Status in August 2025 and meets the QDMTT Safe Harbour conditions. The lists of Pillar 2 territories, qualifying domestic top-up taxes, and accredited QDMTTs for UK purposes are maintained under the Multinational Top-up Tax (Pillar Two Territories, Qualifying Domestic Top-up Taxes and Accredited Qualifying Domestic Top-up Taxes) Regulations 2025 (SI 2025/406), as amended, and published through HMRC's reference notices. Where the UAE QDMTT is accredited and the safe harbour election is made, the UK MTT treats the UAE members of a UK-parented or UK-connected group as having no top-up amount. UK Multinational Top-up Tax does not then charge UAE income; the UAE collects the 15% floor through its own DMTT, and the UK accepts that collection as discharging the Pillar Two liability on UAE profit. The UAE DMTT framework sets out the UAE-side computation that produces the discharging charge.
The condition. The discharge is by election and depends on the QDMTT being accredited and the safe harbour not being switched off for the relevant members. The 2025 amendments themselves include a provision that disapplies another jurisdiction's QDMTT safe harbour where that QDMTT does not apply to securitisation vehicles, which is an example of the safe harbour being switched off in a defined case. A UK group relying on the UAE safe harbour to keep UAE income out of UK MTT has to confirm the UAE QDMTT is accredited for the period, make the election, and hold the UAE-side evidence (the UAE GIR data demonstrating the QDMTT computation) that supports it. Where the election is not available or not made, the UK MTT computes the UAE income at 15% under the IIR, and the group faces a UK charge on income the UAE has also taxed until the credit and safe harbour mechanics resolve it.
The UTPR overlay. For FY2024, the first period for a calendar-year group, only the IIR within MTT applied; the UTPR did not apply until periods beginning on or after 31 December 2024. The UTPR is the backstop that allocates a top-up where no IIR has captured it, and from FY2025 onward it is part of the UK computation. For UAE income, the safe harbour discharges both the IIR and the UTPR exposure where the election is made, because the accredited QDMTT is accepted as the collecting mechanism. The corridor consequence is that the UAE QDMTT, properly evidenced, keeps UAE income out of both UK charging mechanisms.
Five patterns produce most of the early-stage failures we observe in UK Pillar Two files as the first cycle runs through 2026.
Trap 1: treating the registration deadline as the filing deadline. The most common timing error is to assume the 30 June 2026 first-filing date is the first obligation. It is not. The filing member must register within 6 months of the end of the first qualifying period (HMRC manual MTT51400), which for a calendar-year group first in scope for FY2024 is 30 June 2025, a full year before the first return. A group that organises its whole Pillar Two project around the 2026 filing date has already missed the 2025 registration deadline. The architectural answer is to treat registration and filing as two clocks: register within six months of the first period-end, file within the 15 or 18-month window, never before 30 June 2026.
Trap 2: filing nothing because the top-up tax is nil. A group whose every territory already taxes above 15% assumes it has no Pillar Two obligation. The assumption is wrong. The self-assessment return is required from all registered groups, including groups with no MTT liability and groups with no responsible UK members (HMRC manual MTT53010). The information return is required for every qualifying period. The liability can be zero while the filing obligation is absolute. The architectural answer is to register and file on the basis of being in scope, not on the basis of expecting a charge; the nil computation still has to be filed and self-assessed.
Trap 3: conflating the information return with the self-assessment return. The information return reports the GloBE data for every territory; the self-assessment return fixes the group's and each member's liability (HMRC manuals MTT52010, MTT53010). They are two filings under two parts of Schedule 14. A UK sub-group of a foreign-headed multinational can discharge the information return by an overseas return notification where the GIR is filed in the parent jurisdiction with a qualifying authority, but it cannot discharge the self-assessment return that way: the self-assessment return is always a UK filing. A group that files the GIR abroad and assumes the UK obligation is complete has missed the UK self-assessment return.
Trap 4: missing the split commencement of the 2025 amendments. Most of the 2025 amendments take effect for accounting periods beginning on or after 31 December 2025, but the change to pre-regime deferred tax assets takes effect for periods ending on or after 21 July 2025. A first-time filer that applies a single commencement date to the whole 2025 measure can misstate the deferred tax position for a period that ends after L-day 2025 but begins before 31 December 2025. The architectural answer is to read the 2025 amendments provision by provision against the period being filed, and to treat the deferred tax asset change as reaching back into earlier-beginning periods that end after 21 July 2025.
Trap 5: relying on the UAE safe harbour without making the election or holding the evidence. The UAE QDMTT Safe Harbour keeps UAE income out of UK Multinational Top-up Tax, but only by election and only where the UAE QDMTT is accredited and the safe harbour is not switched off for the relevant members (HMRC manual MTT15110). A group that assumes UAE income is automatically outside UK MTT, without making the election and without holding the UAE GIR data that demonstrates the UAE QDMTT computation, has no evidenced basis for excluding the UAE income. Where the election fails or the evidence is absent, the UK IIR computes the UAE income at 15% and the group faces a UK charge on income the UAE has also taxed. The architectural answer is to make the safe harbour election for each relevant UAE member, confirm the UAE QDMTT is accredited for the period under SI 2025/406, and hold the UAE-side evidence as part of the UK filing file.
The common feature of the five traps is that the UK top-up tax is treated as a single annual event rather than as a multi-limb obligation with separate clocks for registration, information reporting, self-assessment, and payment, and a cross-jurisdictional dependency on the UAE and Irish filings. Treated as a single event, each limb is a separate way to fail. Treated as an architecture, the limbs are one programme run once and filed on schedule.
The UK top-up tax filing does not stand alone. For a corridor group operating across two or three of the jurisdictions, the Pillar Two filings stack across 2026 and 2027, and the UK filing is the first to fall due.
The UK leg. Multinational Top-up Tax and Domestic Top-up Tax under Part 3 and Part 4 of Finance (No. 2) Act 2023. First filing for a calendar-year group (FY2024) due 30 June 2026 under the 18-month extension landing on the floor. Standard 15-month window thereafter (FY2025 due 30 June 2027; FY2026 due 31 March 2028). UTPR within MTT effective for periods beginning on or after 31 December 2024, so it enters the computation from FY2025.
The UAE leg. The UAE Domestic Minimum Top-up Tax under Cabinet Decision No. 142 of 2024 applies to financial years starting on or after 1 January 2025. First filing 18 months from period-end (transitional), so 30 June 2027 for FY2025 calendar-year groups; the UAE Corporate Tax return for the same year is due separately, 9 months from year-end, on 30 September 2026. The procedural detail of the UAE first cycle is set out in the UAE DMTT first-filing analysis. The UAE QDMTT, accredited for the UK safe harbour, discharges UK MTT on UAE income by election.
The Ireland leg. Ireland's Pillar Two under Part 4A TCA 1997 (Finance (No. 2) Act 2023) applies the IIR for periods commencing on or after 31 December 2023, the UTPR from 31 December 2024, and the domestic top-up tax from 31 December 2023. The first IIR and domestic top-up filing for Irish in-scope groups with FY2024 year-ends is due 30 June 2026, the same date as the UK first filing, and Pillar Two registration was due 28 February 2026. The Irish leg of the corridor, and the Ireland-UAE treaty network that sits beneath it, is set out in the Ireland holding-company analysis.
The corridor sequence for a UK-parented group with UAE and Irish members runs:
The architectural answer for corridor groups is to run a single GloBE Income workflow per period that produces the data for every jurisdiction's filing, file the GIR centrally where the central-filing route is available, and discharge the local information-return obligations by notification where a qualifying authority has the return. The UK self-assessment return, the UAE Top-up Tax Return, and the Irish return are then produced from the same workpapers but filed locally on their respective dates. The UK filing is the first of the three to fall due, which makes the UK first cycle the pacing item for the whole corridor Pillar Two programme.
For a calendar-year group whose first in-scope period is the year beginning 1 January 2024 (FY2024), the first information return and first self-assessment return are due 30 June 2026. The 18-month extension that applies to the first accounting period would land on 30 June 2026, which is also the statutory floor below which no filing date can fall (HMRC manual MTT53010). No UK Multinational Top-up Tax or Domestic Top-up Tax return is due before 30 June 2026, whatever the period-end. The payment date aligns with the filing date, so the first payment is also due 30 June 2026.
The 2025 amendments revise Part 3 (Multinational Top-up Tax) and Part 4 (Domestic Top-up Tax) of Finance (No. 2) Act 2023 to align UK law with the OECD Administrative Guidance published in January 2025. They were published in draft on 21 July 2025, confirmed at the Budget of 26 November 2025, and carried in the Finance (No. 2) Bill 2024-26. They take effect for accounting periods beginning on or after 31 December 2025, except the change to pre-regime deferred tax assets, which takes effect for periods ending on or after 21 July 2025. The changes are technical (non-material member simplifications, deferred tax adjustments, securitisation carve-outs, REIT adjustments for DTT, election deadline extensions); the 15% charge itself is unchanged, and HMRC scores the measure as nil for Exchequer impact.
Multinational Top-up Tax (Part 3) is the UK's Income Inclusion Rule and, from periods beginning on or after 31 December 2024, also contains the Undertaxed Profits Rule; it charges a top-up on the low-taxed income of the foreign members of a UK-connected group. Domestic Top-up Tax (Part 4) is the UK's Qualified Domestic Minimum Top-up Tax; it charges a top-up on UK members whose aggregate UK effective tax rate is below 15%, so the UK rather than another territory collects the top-up on UK profit. Both took effect for accounting periods beginning on or after 31 December 2023, both use the EUR 750 million threshold, and both are administered through the single code in Schedule 14. DTT additionally reaches wholly domestic groups and single entities that meet the threshold.
The filing member must register with HMRC no later than 6 months after the last day of the accounting period in which the group first became a qualifying multinational group (HMRC manual MTT51400). For a calendar-year group first in scope for the period ending 31 December 2024, registration is due by 30 June 2025, a full year before the first return. The filing member is the Ultimate Parent Entity by default, even where it is overseas, though a group with a foreign parent may nominate a UK member. A single registration covers both Multinational Top-up Tax and Domestic Top-up Tax. Agents cannot register on the group's behalf.
The information return is the UK expression of the GloBE Information Return: it reports GloBE Income, Covered Taxes, effective tax rates, top-up amounts, and elections for every territory in which the group operates (HMRC manual MTT52010, Part 4 Schedule 14). The self-assessment return fixes the group's total liability and each member's liability and is required from every registered group, including those with no liability (MTT53010, Part 5 Schedule 14). Both are due within 15 months of period-end, 18 months for the first period, never before 30 June 2026. Where the information return has been filed with a qualifying authority abroad, the UK information-return obligation can be met by an overseas return notification, but the self-assessment return is always a UK filing.
Yes. The self-assessment return must be submitted by all registered groups, including groups that have no Multinational Top-up Tax liability for the period and groups that have no responsible members in the UK for the period (HMRC manual MTT53010). The information return is likewise required for every qualifying period. A group can submit a below-threshold notification in place of a self-assessment return only for a period in which it has fallen below the EUR 750 million threshold. Being above the threshold with a nil top-up computation does not remove the filing obligation; the nil position still has to be returned and self-assessed.
The UAE DMTT under Cabinet Decision No. 142 of 2024 achieved OECD Transitional Qualified Status in August 2025 and is an accredited Qualified Domestic Minimum Top-up Tax for UK safe harbour purposes (the lists are maintained under SI 2025/406). Where the QDMTT Safe Harbour election is made, the UK Multinational Top-up Tax treats the UAE members as having no top-up amount, so UK MTT does not charge UAE income (HMRC manual MTT15110). The UAE collects the 15% floor through its own DMTT and the UK accepts that as discharging the Pillar Two liability on UAE profit. The discharge is by election and depends on the UAE QDMTT being accredited for the period, the safe harbour not being switched off for the relevant members, and the UAE-side evidence being held to support the election.
For a UK-parented calendar-year group, the UK MTT and DTT first filing for FY2024 falls on 30 June 2026, alongside the Irish first IIR and domestic top-up filing for FY2024. The UAE Corporate Tax return for FY2025 is due 30 September 2026, and the UAE DMTT first filing for FY2025 falls on 30 June 2027 under the UAE transitional window, the same date as the UK second filing for FY2025. The UK first filing is the earliest of the corridor Pillar Two obligations, which makes it the pacing item. The efficient answer is a single GloBE Income workflow that feeds the UK, UAE, and Irish returns, with the GIR filed centrally where available and local information-return obligations met by notification.
The UK top-up tax has been live since accounting periods beginning on or after 31 December 2023, amended three times, and aligned to the January 2025 OECD guidance by the 2025 measure. The first return for a calendar-year group falls on 30 June 2026, and the registration that precedes it fell due on 30 June 2025. The group that has not yet registered is not preparing for the first filing; it is already late for the step before it.
Ireland completed its territorial corporate tax framework on 1 January 2025 with the dividend participation exemption under section 831B TCA 1997 alongside the capital gains exemption under section 626B. Combined with the Ireland-UAE DTA 2010 and the 12.5% trading rate, Ireland is now a third corridor leg.
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