Why Your Tax Code Changed to 1131N (2026 Marriage Allowance Guide)
A tax code change can trigger instant anxiety. The letter from HM Revenue & Customs has landed. Your payslip looks different. The number 1257L disappears, and the 1131N tax code appears instead. It feels technical. Slightly ominous. In reality, the 1131N tax code is usually linked to Marriage Allowance — but in 2026, frozen thresholds,

