“If your income is under the personal allowance, currently £12,570, you may be eligible to apply for Marriage Allowance. This allows you to transfer £1,260 of your personal allowance to your husband, wife or civil partner, if they are a basic rate taxpayer, and can reduce their tax by up to £252 each tax year based on current rates.
HMRC allow eligible claims to be backdated to include any tax year since 5 April 2018 meaning further savings could be available.”