“Balancing payment” due when all tax is already deducted at source

AFF8879

I’m having to complete an online self-assessment as my total employment income exceeded 100k for the prior tax year. I’ve gone through all the steps on HMRCs website and it’s saying I owe a figure of around £250 as “2021-2022 balancing payment”. 

What I don’t understand is that all my income is taxed at source - I only receive employment income (and an ISA which is not declarable). 

This is my first time doing a SA so maybe I’m missing something, I didn’t think they would need to estimate tax due as it’s all taken via PAYE. Plus all my income tax/pay figures have been entered directly from my P60, payslip etc so it’s not as though I incorrectly entered salary, bonus etc 

am I missing something?

Dazed_and_C0nfused

Yes you're missing the fact that PAYE is a provisional attempt to collect the correct amount of tax.

Where a Self Assessment return is necessary that is what determines the actual amount of tax payable.

Chances are your PAYE tax code allowed slightly more allowances than it transpires were actually due.

Have you checked how accurate the current tax years tax code is?

[Deleted User]

What was the tax code on the P60?