Where the rates come from

Rates for 2026/27 come from GOV.UK. Scottish income tax comes from mygov.scot. The tax rates page lists each figure with its source and the date we last checked it. The rates changelog lists what changed from the year before.

How the rates stay current

A script reads each source page and, when a page has changed, opens an issue for us. It never changes a figure itself.

A person then reads the page, updates the figure and its tests, and records the new check date.

How a day rate becomes a year

A year is 52 weeks. At 5 days a week that is 260 days, less 28 days off, which gives 232 paid days. Time off is unpaid. You can change the days a week, the contract length and the days off.

How each setup is taxed

Limited company, outside IR35: you take a salary, and the company pays the rest out as dividends. Corporation tax, employer NI, income tax, NI and dividend tax all apply.
Umbrella company: the umbrella's fee and employer NI come out of your rate. Income tax and NI are then charged on what is left as pay.
Inside IR35: the whole rate is taxed as pay through PAYE. By default the agency pays employer NI on top.
Sole trader: income tax on profit, plus Class 4 NI.
Permanent employee: salary, income tax and employee NI.

How we check the maths

Hand-worked examples from the official rules. Each figure must match within £1.
A second calculator, written separately from the GOV.UK rules, compared with Modulas on 4,000 cases. It must match within £1.
Random checks, for example that a higher day rate never lowers take-home, except where the rules say it can.

Figures are rounded to the pound.

If a figure looks wrong

Use 'Send feedback' at the foot of any page to tell us what you entered and what Modulas showed. We'll look into it. The limits page lists what Modulas assumes and leaves out.