Tax Code Guide
M1
Month 1 Emergency Tax
What does this code mean?
Suffix M1 (or W1 for weekly pay) means your tax is calculated only on what you earn in the current pay period, not cumulatively for the year. This "non-cumulative" basis often results in overpaying tax because your full personal allowance is not spread across the year. It is usually a temporary measure until HMRC issues your correct code.
Emergency Tax Warning
This is often an emergency or temporary tax code. You might be paying too much tax while on this code.
Who gets this code?
New employees, people changing jobs, or emergency tax situations. Almost always leads to overpayment that you can claim back.
Is it correct?
Check your latest P45 or Payslip to see if this matches your current situation.