Accountants and individuals still need a proper SA100 workspace: HMRC pages, calculation, SA302-style reports and a filing desk.
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About Self Assessment Software
Self Assessment Software is dedicated SA100 production from Swift Catalyst Ltd. Tax returns for people — not a full practice suite.
In short
Self Assessment Software is UK year-end Self Assessment software from Swift Catalyst Ltd. We build the SA100 desk — forms, calculation, reports and HMRC filing — for accountants and individuals. Prepare free; pay when you file. We do not sell bookkeeping, corporation tax, payroll or a practice suite.
Why a dedicated Self Assessment desk
Most “tax software” bundles the return with bookkeeping, CT600 or a full practice suite. That raises the price and dilutes the year-end job.
If you only need Self Assessment, you should not have to buy invoices, corporation tax or payroll seats to get there.
Individuals pay per tax year when they file. Practices buy filing credits. Drafting never uses a credit.
Saying what we will not build is how the price and the product stay on Self Assessment.
What we build
One workspace for the year-end return — the same desk a practice or an individual uses after sign-in.
Main return plus the supplementary pages that apply, and the partnership SA800 path.
Combined tax calculation, SA302-style estimate and a detailed schedule you can print.
Draft → review → approve → submit. Status and snapshot for that client tax year.
Each login sees only its workspace. Sensitive identifiers are encrypted at rest.
Commercial model
How you buy
Prepare every return free. You pay only when that tax year is ready to file.
Employment & investment £39 · Self-employed & property £49 · Partnership £69 — all ex VAT, once per tax year.
Filing credits: 10 for £179 · 25 for £349 · 50 for £599 · 100 for £999 (ex VAT). One credit = one client tax year. Unlimited logins.
Public plans are pay-when-you-file. There is no monthly taxpayer-cap subscription on this site.
When you have paid for that tax year (or used a credit), amendments for the same return year are included.
Legal entity
The company behind the product
Self Assessment Software is a service of Swift Catalyst Ltd, a UK limited company.
- Trading name
- Self Assessment Software
- Legal name
- Swift Catalyst Ltd
- Company number
- 17130521
- VAT number
- 517276581
Scope
What we will not build
If you need the row below, buy that product — then keep Self Assessment here. That is how the price stays on the return.
No invoices, bank feeds or VAT returns. Keep FreeAgent, Xero or QuickBooks for the ledger.
No CT600, iXBRL or Companies House filings.
This is software only. You stay responsible for the figures you file with HMRC.
Year-end Self Assessment is included. Quarterly Income Tax updates are a later add-on.
vs Bookkeeping · MTD for Income Tax · Compare TaxCalc & Capium
Next
Explore the product
Forms, calculation, reports and filing desk.
From £39 when you file — prepare free.
Unlimited logins and filing credits.
File your own SA100 from £39.
Organisation isolation and encryption.
Demo, credits, or a question.
FAQs
About us — questions answered
Who makes Self Assessment Software?
Self Assessment Software is a service of Swift Catalyst Ltd (Company No. 17130521, VAT No. 517276581), a UK limited company.
What does Self Assessment Software do?
It is dedicated UK year-end Self Assessment software: SA100 and supplementary pages, partnership SA800, combined calculation, SA302-style reports and an HMRC filing desk for accountants and individuals.
Is it a practice suite or bookkeeping app?
No. It does not include bookkeeping, corporation tax, payroll, VAT or Companies House. Those belong to other products — that is how the price stays on Self Assessment.
How much does it cost?
List prices exclude VAT. Individuals: Employment £39, Self-employed & property £49, Partnership £69 per tax year when you file. Accountants: filing credits from £179 for 10. Prepare free — no card to start.
Where can I ask a question?
Use the contact form. We reply within one business day about demos, accountant credits, or Self Assessment for your own return.
Prepare free
Ready to try the desk?
Create an account free. Prepare the return with no card, and pay only when you file that tax year.