Glossary · UK
What is Married Couple's Allowance?
An Income Tax allowance available to married couples or civil partners where at least one partner was born before 6 April 1935, reducing the couple's combined tax bill rather than their taxable income directly.
Full Definition
Married Couple's Allowance (MCA) is an Income Tax allowance available only where one spouse or civil partner in the couple was born before 6 April 1935 -- a group that, by definition, is now elderly, so the allowance is claimed by a shrinking and specific population rather than married couples generally (who instead may be able to use the separate, much more widely available Marriage Allowance). Unlike the ordinary Personal Allowance, which reduces taxable income, MCA works as a fixed reduction to the tax bill itself, calculated at 10% of the allowance amount. For 2026/27, the maximum MCA is set each year by HMRC and uprated in line with the relevant inflation measure, with a minimum amount that applies even where the higher-earning partner's income is well above the income limit for tapering. MCA is tapered away for higher-income claimants: where the person entitled to claim it (normally the husband in older marriages, but reforms allow the couple to nominate who claims, and civil partners and same-sex married couples are treated identically) has income above a set income limit, the allowance is reduced by 1 for every 2 of income above that limit, down to the minimum amount, in a similar tapering mechanism to the Personal Allowance income limit taper (though MCA's taper threshold and reduction rate are calculated separately from the Personal Allowance's own 100,000 to 125,140 taper). Couples can choose how to split the minimum amount of MCA between them, or transfer any unused portion to the other spouse or civil partner, using HMRC forms 575(T) or 18 depending on the situation. Because eligibility is restricted to couples where a partner was born before 6 April 1935, the number of people able to claim MCA falls each year, and it should not be confused with the separate Marriage Allowance, which is available to any married couple or civil partnership where one partner is a non-taxpayer and the other a basic-rate taxpayer, and which works by transferring 10% of the Personal Allowance rather than giving a direct tax reduction.