About AssessTally
AssessTally is an independent, advertising-supported website. AssessTally turns official UK Income Tax, National Insurance, Self Assessment deadline, payment-on-account and penalty figures into clear browser calculators, so people can plan a bill before they file.
What we publish
Five tools — a 2025/26 and 2026/27 Income Tax and Class 4 NI estimator, a payments-on-account helper, a student-loan repayment estimator, a late-filing and late-payment penalty estimator, and a UK tax-code decoder — plus original guides. We do not file returns or give tax advice.
How we research
Figures are taken from official GOV.UK publications that we re-fetched when this edition was built, including the Income Tax rates and allowances page (updated 6 April 2026), Budget 2026 Annex A (updated 5 November 2026), the National Insurance contributions rates page (updated 6 April 2026), the employer rates pages for 2025/26 and 2026/27, and HMRC’s pages on deadlines, payments on account, penalties and tax codes. We summarise in our own words and link the source on each page. NewDeduct and Year-End Moves on dollarfinch.com are US federal tax tools; they are not used for UK Self Assessment. Every figure that comes from a third party is linked at the bottom of the page where it is used, and every page shows when it was last reviewed. If a carrier, retailer or organisation changes its published information, the official source wins over anything on this site.
How the tools work
Calculations run in your browser from what you enter. Nothing is uploaded to AssessTally. Results are estimates based on the method described on each page; HMRC’s own calculation on your filed return is the one that matters.
How we make money
AssessTally shows advertising (Google AdSense) and does not accept payment from insurers, brokers, banks or any company in exchange for coverage in our guides. We do not sell leads, and we do not sell or recommend any specific insurance policy or financial product.
Corrections
If you spot an error, tell us through the contact page. We correct factual mistakes quickly and update the “last updated” date when we do.