UK Self Assessment Tax Calculator
Stop guessing what you'll owe HMRC.
- Opens in any browser — no Excel, no Google Sheets account required
- Fully offline — your financial data never leaves your device
- One-time purchase — no subscription, ever
- See every calculation band by band — nothing hidden inside a locked formula
- Every figure mapped to its SA100 / SA103 tax return box
You'll be taken to Etsy to complete your purchase securely.
Overview
Stop guessing what you'll owe HMRC. This offline HTML app calculates your estimated Income Tax, National Insurance, dividend tax and student loan repayments — and shows you exactly which box each figure goes in when you file.
Built for UK sole traders, freelancers, and side-hustlers who want the clarity of a professional tax tool without the hassle of Excel licences, Google account sign-ups, or monthly software subscriptions.
Features
- Opens in any browser — no Excel, no Google Sheets account required
- Fully offline — your financial data never leaves your device
- One-time purchase — no subscription, ever
- See every calculation band by band — nothing hidden inside a locked formula
- Every figure mapped to its SA100 / SA103 tax return box
- Automatic Income Tax calculation across basic, higher and additional rate bands
- Class 4 and Class 2 National Insurance calculated automatically
- Dividend tax and savings interest tax, with allowances applied correctly
What's Included
- 1 offline HTML app file (UK_Self_Assessment_Tax_Estimator.html)
- 14-page PDF user guide
- 1-page Quick Start Card
- Personal use licence
- Pre-loaded example/demo data so you can see how it works right away
Screenshots
How It Works
Choose Your App
You've found it — UK Self Assessment Tax Calculator.
Purchase on Etsy
Use the Buy on Etsy button above to complete your purchase.
Download Your Files
Receive the digital files associated with your purchase.
Follow the Setup Guide
Use the included instructions to get started.
Start Using It
Begin organising with UK Self Assessment Tax Calculator.
Compatibility
Desktop & Laptop
Works on both Windows and Mac in a modern browser (Chrome, Edge, Firefox or Safari).
Mobile & Tablet
See the Etsy listing for mobile/tablet compatibility.
Offline Use
Works offline once downloaded — no internet connection is required to use it day-to-day.
Important Notes
Please read before purchasing
No login or account is required to use it. One-time purchase — no subscription or recurring fees. This is a digital product — no physical item will be shipped. All sales, checkout and delivery are currently handled by Etsy.
Need Help?
Visit our Support page for setup help and troubleshooting, or get in touch if you have a question about this product.