Tax Code BR M1 Explained

What does BR M1 mean?

BR stands for "Basic Rate" and is one of the simplest UK PAYE tax codes to read: every penny of income from the employment carrying this code is taxed at the basic rate of 20%, with zero personal allowance applied. There is no tax-free amount, no smoothing across bands, and no W1/M1 quirk to worry about — it is a flat 20% on every pound. BR almost always appears on a second job, a pension that runs alongside earnings, or a freelance retainer paid via PAYE, because HMRC has already allocated your £12,570 personal allowance to your main source of income. In those cases BR is correct and produces the right total tax across your combined earnings. The code becomes a problem when it is applied to your only job, which can happen if you started a new role without a P45, ticked Statement C on the starter checklist, or HMRC has lost track of your other PAYE income. In that situation you will be overpaying tax every payday and can claim a refund either through a corrected code (most refunds are paid back automatically through payroll once HMRC issues a P9) or through a P800 reconciliation at the end of the tax year. The M1 suffix changes how the code is applied. Instead of recalculating against year-to-date earnings every payday (the normal cumulative method), payroll treats each pay period as a fresh start. You receive 1/52nd (W1), 1/12th (M1) or one slice (X) of your tax-free allowance and basic-rate band each period, and any unused allowance from earlier in the year is ignored. That stops a refund being issued before HMRC has confirmed your figures, but it can leave you slightly overpaid until a cumulative code is reissued. M1 codes are almost always temporary holding codes that resolve within one or two pay cycles after your first FPS submission reaches HMRC.

Breakdown of the code

• BR

  Letter pair

  Basic Rate — flat 20% on every pound, with no tax-free allowance applied at this source.

• M1

  M1

  Non-cumulative monthly basis. Each pay period is treated independently — no smoothing across the year.

Worked example

Second job — Saturday retail role at £8,000/year on £8,000 (paid monthly).

£8,000 × 20% = £1,600/year. Correct because the £12,570 allowance is allocated to the main job.

Who should be on BR M1?

• New starters who could not provide a P45 and completed a starter checklist
• Employees whose previous employer reported their leaver pay late
• People returning to PAYE after self-employment or working overseas
• Cases where HMRC has paused a cumulative calculation pending a record review

Common problems

• Bonuses and one-off payments are taxed harder than under a cumulative code because unused allowance from earlier months is ignored.
• The code persists for three or more months — usually a sign HMRC has not received the FPS submission needed to reconcile your record.
• You have switched jobs and your former employer issued the P45 late, so the W1/M1/X code stays in place longer than it should.

What to do if BR M1 looks wrong

1. Provide your employer with a P45 from your previous job, or complete a starter checklist accurately (Statement A, B or C).
2. Wait one or two pay cycles — most emergency codes auto-correct as soon as HMRC receives the first FPS submission from your new employer.
3. If the code persists into a third payslip, sign in to your personal tax account and confirm both employments are listed correctly.
4. Phone HMRC on 0300 200 3300 quoting the date you started and the date your last job ended — they can issue a cumulative P9 the same day.
5. Once a cumulative code is reissued, any overpaid tax is refunded automatically through your next payslip.