The unused allowance next door: a 2026-27 Marriage Allowance audit

Marriage Allowance is a small relief with a long memory. It can be claimed for the current tax year and up to four earlier ones, yet many couples assume the door is closed because of a pay rise, a pension, or the simple fact that neither partner files a self-assessment return. In 2026-27 the maximum transfer is 10% of the personal allowance: £1,257. For a basic-rate recipient, that is a tax reduction of up to £252. The figure is modest, but the administrative point is larger: the claim is tested year by year, and a change in either partner’s income can make a valid claim invalid.

What the allowance actually moves

Marriage Allowance is not a cash payment. It is a transfer of part of the personal allowance from one spouse or civil partner to the other, followed by a tax reducer worth 20% of the transferred amount. The transferor must have unused personal allowance, and the recipient must be liable to income tax at the basic rate. The maximum transfer is £1,257 in 2026-27, subject to the transferor having enough unused allowance; the maximum tax saving is £252.

The relief is available to married couples and civil partners, not to unmarried couples living together. That distinction is often missed in informal discussions, but it is fundamental. A couple who have lived together for years without marrying or forming a civil partnership cannot use the allowance, however financially intertwined their lives may be.

A common misconception is that the lower earner must have no income at all. That is not correct. What matters is that the transferor’s income is below the personal allowance and that the recipient remains a basic-rate taxpayer. A partner with a small pension, modest savings income or part-time earnings may still have unused allowance to transfer. Equally, a partner with no income can transfer, provided the other conditions are met.

Why eligible couples talk themselves out of it

The first assumption is that the claim is automatic. It is not. HMRC does not usually apply Marriage Allowance simply because a couple are married. One partner must start the claim, and the other must confirm the transfer. Until that happens, the relief is not in the PAYE code and not in any self-assessment calculation.

The second assumption is that a single bonus or a busy year has closed the door permanently. Eligibility is assessed for each tax year separately. A recipient who crosses into higher-rate territory in one year may still have a valid claim for earlier years. Conversely, a couple who claimed successfully in a year when both were basic-rate taxpayers may find that a later promotion, a maturing pension or a one-off dividend takes the recipient above the basic-rate limit. That does not necessarily invalidate the whole claim history, but it does mean the current year needs review.

The third assumption is that a self-assessment return is required to claim. In many cases it is not. A couple who are not otherwise within self-assessment can use the online Marriage Allowance service. The claim should not, by itself, create a filing obligation. Where one partner already completes a return, the relief needs to be reflected in the return or in the coding notice, and the confirmation should be kept with the tax records.

The year-by-year test and the higher-rate trap

Marriage Allowance is not a lifetime status. It is a series of annual claims. For each year, the transferor must have income below the personal allowance, and the recipient must not be liable at the higher or additional rate. If the recipient’s income exceeds the basic-rate limit, the claim is not available for that year. If a claim has already been applied through a PAYE code, HMRC may adjust the code or recover the benefit through the assessment.

The practical risk is a mid-year change. A pay rise in September, a bonus in March or a large dividend paid before 5 April can alter the final position for the whole year. A couple who claimed in April on the basis of a basic-rate salary may discover in January that the recipient’s total income has crossed the threshold. The remedy is not to ignore the change. The claim should be reviewed against the final figures, and any over-applied relief should be corrected before HMRC does it through a coding adjustment.

Pension contributions can complicate the picture. Relief at source contributions and Gift Aid donations can extend the basic-rate band, which may preserve eligibility where income would otherwise appear to cross the threshold. That does not mean a claim should be made on hope. It means the whole-year figures, including reliefs and allowances, should be checked before a claim is cancelled or allowed to run.

Backdating without a self-assessment return

A claim made in 2026-27 can normally be backdated to 2022-23, 2023-24, 2024-25 and 2025-26, in addition to the current year. The oldest year is time-limited: 2022-23 remains in the window until 5 April 2027. A couple who have been eligible for several years but never claimed may therefore be able to recover more than the current year’s £252. The exact amount depends on each year’s personal allowance and the recipient’s tax position.

Backdating does not require a self-assessment return in every case. The online service can handle claims for earlier years, and HMRC may issue a repayment or adjust the tax code. Where a return is already in scope, the earlier-year claim should be checked against the return position so that the same relief is not claimed twice. Records of the claim, the confirmation and any coding notices should be retained.

A word of caution: backdating is not a reason to claim carelessly. If the recipient was a higher-rate taxpayer in one of the earlier years, that year should be excluded. The online process may prompt for information, but the responsibility for confirming eligibility remains with the couple.

Pension relief, child benefit and the wider picture

Marriage Allowance interacts with two areas that often surprise couples. The first is pension relief. Contributions made under relief at source can affect the point at which higher rates begin, so a recipient whose income is close to the basic-rate limit should check the final position rather than rely on the salary alone. The second is the High Income Child Benefit Charge. Marriage Allowance is a tax reducer; it does not reduce adjusted net income. It will not, by itself, keep a family below the £60,000 threshold at which the child benefit charge begins, nor does it remove the charge between £60,000 and £80,000. Couples near those figures should model the child benefit position separately.

These interactions do not make the allowance unsuitable. They simply mean the claim should be reviewed alongside the rest of the household’s tax position, particularly where income is variable or close to a threshold.

A short online checklist

Before starting the claim, both partners should confirm that they are married or in a civil partnership, that the transferor has unused personal allowance, and that the recipient is a basic-rate taxpayer for the year in question. Gather both National Insurance numbers and have the relevant income figures to hand for any backdated years. The partner with unused allowance normally starts the online claim and the other confirms the transfer.

After submitting, keep the confirmation. Check the next coding notice or self-assessment calculation to confirm that the relief has been applied. If either partner’s income changes materially, revisit the claim rather than waiting for HMRC to notice. And if a claim is made for earlier years, check that each year is separately eligible; a successful current-year claim is not proof that every earlier year qualifies.

Marriage Allowance rewards a five-minute administrative habit, but only where the annual test is respected. For couples who have overlooked it, the backdating window is still open for several years. For couples already claiming, the task is quieter: check the figures, watch the thresholds, and keep the confirmation. That is the PrimoTax approach to a relief that is small in value but easy to mismanage.