These figures are correct for the 2021/22 tax year.
1131N is a common tax code for people who have taken advantage of the Marriage Allowance for the 2021/22 tax year.
What does it mean?
Nearly everyone is entitled to a tax-free personal allowance, which means that a certain amount of your earnings each year are paid to you without being taxed. For most people this amount is £12,570.
If you earn less than this, the Marriage Allowance allows you to transfer 10% of your allowance to your wife, husband or civil partner. This increases their own tax-free earnings, meaning as a couple you don’t lose all of the benefit.
If your tax code is 1131N, it means that you have transferred £1,257 of your personal allowance to your partner, leaving you with an allowance of £11,313.