When BR is correct
HMRC uses BR for situations where your personal allowance is already being applied somewhere else:
- Second jobs — your main job uses 1257L (which applies the £12,570 allowance); your second job uses BR (taxing every pound at 20%)
- Private pensions while you're still working — the pension provider runs BR because your allowance is on your salary
- Temporary transitions — sometimes BR is applied briefly when you change jobs without a P45
When BR is wrong
BR is incorrect if it's on your only source of income. With no other taxable income and no other pension, your code should be 1257L (or a variation that still includes the allowance).
If BR is on your only job, you're effectively paying 20% tax on the first £12,570 you'd normally get tax-free — costing roughly £209 a month or £2,514 a year more than the standard code.
The fix
The fastest route is your HMRC Personal Tax Account at gov.uk/personal-tax-account. It shows the live tax code at every employer and the reasoning behind each. You can correct most issues directly. If the online tool can't resolve it, call HMRC on 0300 200 3300.
Refunds for overpaid tax come automatically once the code is corrected — either through your next payslip (if mid-tax-year) or via a P800 letter from HMRC (if the year has ended).