How much tax should you set aside as a sole trader
The honest answer is “enough that January does not ruin you.” Here is how to turn that vague goal into a number you can automate for the 2026/27 tax year.
Why percentages mislead
Rules of thumb like twenty or twenty-five percent are useful on day one because they beat saving nothing. They fail quietly when you cross into higher-rate territory, when you add PAYE income on top of self-employment, or when you register for VAT and start holding output tax that is not yours. Treat a flat percentage as training wheels, not cruise control.
Start from an annual liability, not from vibes
Estimate your profit for the year, run it through a tax calculator, and read off the total tax and National Insurance you expect. Divide that total by the number of weeks you actually expect to get paid across the year. That weekly figure is your mechanical target — easier to defend to yourself when a quiet month tempts you to skip a transfer.
Separate pots beat one big balance
Open a dedicated instant-access savings account labelled for tax. Optionally add a second for VAT if you are registered. Move money the day an invoice clears, not at month end when the balance looks “available.” Behaviourally, friction is the point: you want spending your tax money to feel like borrowing, not like reallocating pocket change.
Turn your estimate into a habit
Start with your annual bill, then refine take-home and PAYE interactions if needed.
Revisit the figure when the story changes
New client, lost client, rate rise, or equipment purchase — each changes profit. A quarterly fifteen-minute check (recalculate, adjust standing order) saves you from discovering drift only when HMRC writes. If you use an accountant, send them updated forecasts before year-end, not only after the year has closed.
If you still hate saving, automate the pain away
Standing orders beat willpower. Schedule the transfer for the day after you usually invoice, match it to the percentage our calculator outputs, and refuse “temporary” pauses unless you have rebuilt the annual estimate. Treat skipped transfers like skipping rent — allowed in a genuine emergency, not as a monthly lifestyle.