I think this would help more accurately model UK PAYE (pay as you earn).

Currently to simulate PAYE I have to work out an effective rate resulting from application of the tax bands and enter that as tax withholding % I never seen to get it spot on and there always seems to be a rebate or extra tax to pay the next year.

FTR, the Australian for withholding is:

• You nominate your primary salary as eligible for progressive taxes, and the withholding is calculated as though this is your only source of income. You can ask your employer to withhold extra, to if you like, to cover anticipated extra income like dividends.
• Secondary salary has withholding of the top marginal rate
• If you get a big tax bill due to passive income, the ATO deems you will have a similar bill next year and you have to pay additional withholding, unless you lodge a variation request to declare circumstances have changed.

It would be handy to mark the primary salary withholding as “automatic”.

It would also be handy to take withholding tax from income on taxable investments.

But for long-term planning the current approach of taking the extra taxes in Year + 1 is not so bad.

Adding my support for this from the Australian perspective 👍

Here is the discussion on Discord about this: https://discord.com/channels/869222901054857216/1297979782704926770/1297979782704926770

This is a much-needed feature, especially for users outside the U.S. In many countries (like the UK, Canada, Australia, France, etc.), income taxes are withheld dynamically from each paycheck during the year based on actual bracket calculations. There is no large “tax refund” or “return payment” the following year, it all happens within the same calendar year.