The freelancer tax mistake that costs £2,000+ (and nobody warns you about)

#freelancing #career #productivity #beginners

You finish your first year freelancing. You file your tax return. You pay what HMRC says you owe.

Then — surprise — they ask for another payment. Same amount. Due immediately.

Payment on Account

If your tax bill is over £1,000 (and less than 80% was collected at source), HMRC makes you pay advance payments towards next year's tax.

Two payments:

31 January — 50% of last year's bill
31 July — another 50%

So if your first year's tax bill is £4,000, your January payment is actually £6,000. The tax itself plus the first payment on account.

Nobody tells you this. Not your mates. Not the YouTube videos. Not even most "first tax return" guides.

The maths that ruins January

Year 1 profit: £35,000
Tax + NI owed: ~£5,200
First payment on account (50%): £2,600
Total due 31 January: £7,800

You budgeted for £5,200. You're £2,600 short. Happy new year.

How to not get caught out

Set aside 30% of everything you earn, not 20%. The extra covers payment on account
Reduce payments on account if this year's income will be lower — use form SA303 or do it through your online account
Use a penalty calculator to see what happens if you're late — landolio.com/tools/self-assessment-penalty-calculator.html
Read the full breakdown — landolio.com/blog/payment-on-account-self-assessment-uk-guide-2026.html

The silver lining

Payment on account means you're essentially pre-paying next year's tax in instalments. So next January is less painful. Assuming you actually set the money aside.

Did anyone warn you about this before your first tax bill? Or did HMRC just... surprise you?

We build free tools for UK freelancers — tax calculators, invoice generators, expense trackers. All free, no signup.