You cannot claim Marriage Allowance if you’re living together but you’re not married or in a civil partnership.
If you or your partner were born before 6 April 1935, you might benefit more as a couple by applying for Married Couple’s Allowance instead. If you and your partner were born on or after 6 April 1935, you may be able to claim Marriage Allowance instead.
Yes, your Personal Allowance will transfer automatically to your partner every year until you cancel Marriage Allowance. You must cancel Marriage Allowance if you become divorced or your income changes for example.
Yes, you can backdate your claim to include any tax year since 5 April 2018 that you were eligible for Marriage Allowance. Your partner’s tax bill will be reduced depending on the Personal Allowance rate for the years you’re backdating.