Royal Mail Overtime: Is HMRC taxing your extra shifts too much?

There is a massive, nationwide myth that "overtime gets taxed at 40%". This is completely false. Overtime is not a special category of money to HMRC. A pound earned in overtime is taxed exactly the same as a pound earned in your base hours.

However, the way the UK tax system uses your tax-free allowance creates a psychological illusion that makes your Royal Mail overtime look like it's being heavily penalized.

The "Tax-Free Allowance" Illusion

Every worker in the UK gets a tax-free Personal Allowance (£12,570 for 2026/27). On a weekly Royal Mail payslip, this equates to £241 of tax-free money every single week.

If you work your normal contracted 35 or 40 hours, the first £241 of your wages is completely untouched by income tax. Only the remaining wages are taxed at 20%.

But when you agree to do an extra 5 hours of Scheduled Attendance (SA) or docket overtime, your entire £241 tax-free allowance has already been used up by your base hours.

This means that every single penny of your overtime pay is exposed to the brutal reality of the 20% Income Tax rate, plus National Insurance (and potentially a 5% pension deduction).

The Math: Why it feels like 30%+ Tax

Let's say your base pay is £450 a week. Your tax is relatively low because £241 of it was tax-free.

Now you do an overtime shift that pays £100 gross. Because your tax-free allowance is already gone, HMRC and the government immediately take a sledgehammer to that £100:

• Income Tax (20%): -£20
• National Insurance (8%): -£8
• Pension (5%): -£5 (if your overtime is pensionable)

Suddenly, your £100 overtime shift only yields £67 in your pocket. It feels like you were taxed at 33%. You weren't penalized for doing overtime; you simply experienced what it feels like to earn money without the protection of a tax-free allowance.

The Higher Rate Danger (Over £50,270)

There is one scenario where doing Royal Mail overtime genuinely pushes you into a higher tax bracket.

If you have a lot of seniority, work massive amounts of SA, or have a side hustle, and your total gross income for the year crosses £50,270, you enter the Higher Rate tax band.

Any overtime you do that pushes your total earnings above that £50k threshold will genuinely be taxed at 40% (plus 2% National Insurance). In this specific scenario, a £100 overtime shift will only put £58 in your pocket. If you are close to this threshold, taking extra shifts becomes mathematically less rewarding.

Is Overtime Pensionable in Royal Mail?

In most companies, overtime is non-pensionable (meaning they don't deduct the 5% pension contribution from it). However, following a major agreement between Royal Mail and the CWU, regular overtime and Scheduled Attendance are often treated as pensionable pay.

While seeing a pension deduction on your overtime reduces your immediate take-home pay, it is actually a massive financial benefit. If you pay 5% into your Royal Mail pension on that overtime, Royal Mail is legally forced to top it up with an employer contribution. It is essentially free money deferred to your retirement.

Frequently Asked Questions