This tool is for illustration only. Tax rules are complex and your personal circumstances may differ. Always confirm figures with HMRC or a qualified tax adviser before acting.
Marriage allowance lets the lower-earning partner in a marriage or civil partnership transfer £1,260 of their unused personal allowance to their spouse. Because the higher earner gets tax relief at 20% on that £1,260, it saves £252 a year in income tax. If you've been eligible for previous tax years and never claimed, you can backdate the claim up to four years — potentially worth over £1,000 in one go.
Around 2.4 million eligible couples haven't claimed. It costs nothing and takes about ten minutes to apply online through HMRC. The lower earner must make the application — not the higher earner. Once set up, the allowance transfers automatically each year until you cancel it. Check with HMRC or a tax adviser if your circumstances are unusual — this tool covers the standard case only.