Why the Autumn Budget 2026 left your tax code unchanged, and what tax codes actually mean
The Personal Tax Allowance
The personal tax allowance in the UK has been £12,570 per year for some time, since 6th April 2021 in fact. This gives the standard tax code of 1257L, with a C prefix for Welsh taxpayers (C1257L) and an S prefix for Scottish taxpayers (S1257L). The Autumn Budget 2026 again saw no changes to the personal tax allowance.
Why does this matter?
Traditionally, the tax code has increased a little each tax year, sometimes more than others. If your pay remains the same but your tax code increases, you will have a little more money before you start paying tax. This has the effect of a small pay rise without costing your employer anything extra.
There are other considerations, such as tax rates and National Insurance, but generally a higher tax code means more money in your pocket, whereas a lower tax code means less.
What is a cumulative tax code?
A cumulative tax code takes into account all taxable pay to date. A non-cumulative tax code only considers the current pay period and applies a proportion of the annual allowance to that period alone.
· 1257L = cumulative
· 1257L Y or 1257L Wk1 = non-cumulative
With a cumulative tax code you may receive a tax refund, whereas with a non-cumulative code only the current period is calculated.
What changes in April?
You may hear about forms such as the P6 and P9, but these are simply tax notices issued by HMRC; the P9 is specific to April. In April, all codes are moved to cumulative unless HMRC has issued a different code, and it is far more unusual to have a non-cumulative code at that point.
Are tax codes complicated?
They are not always straightforward, as there are tax bands as well, and many more of them if you are subject to Scottish tax. There are also other prefixes and suffixes, such as ‘T’ and ‘K’, and codes such as BR or D0. Help and guidance is available, and you can sign in to your personal tax account to see how HMRC has calculated your tax code.