In August 2026, a couple realises they were eligible for Marriage Allowance in earlier tax years but never claimed it. Under HMRC's backdating rules, how far back can they claim?
- They can backdate a claim for up to four earlier tax years, in addition to claiming for the current year, provided they were eligible for Marriage Allowance in each of those earlier years
- Marriage Allowance cannot be backdated at all; it can only be claimed for the current tax year onward from the date the claim is made
- They can backdate a claim for the current year plus one previous tax year, matching the two-year error correction window used elsewhere in Self Assessment
- Backdated claims are unlimited in how many years they can cover, as long as both partners were married or in a civil partnership throughout
Why A? And why not the others?
Correct answer: A. They can backdate a claim for up to four earlier tax years, in addition to claiming for the current year, provided they were eligible for Marriage Allowance in each of those earlier years
HMRC allows a Marriage Allowance claim to be backdated for up to four earlier tax years on top of a claim for the current year, provided the couple was eligible for the allowance in each of those earlier years, which is what the correct option states. The option denying any backdating is wrong because HMRC explicitly permits backdated claims covering several earlier years, not just the current year going forward. The option limiting backdating to one previous year is wrong because it confuses Marriage Allowance's own four-year backdating window with the unrelated one-year amendment window that applies to correcting an already-filed Self Assessment return. The option claiming backdating is unlimited is wrong because HMRC caps how far back a claim can reach at four tax years; eligibility in years beyond that window cannot be claimed for, however long the couple was married or in a civil partnership.
Source: GOV.UK: Marriage Allowance — how it works