Accounting technology / Glossary / Self Assessment software for accountants

What is Self Assessment software for accountants?

Definition

Self Assessment software for accountants prepares and files clients' tax returns to HM Revenue and Customs from one system: the SA100 individual return and its supplementary pages, and in most products the SA800 partnership and SA900 trust returns. It tracks deadlines across clients and can pull client data from HM Revenue and Customs to fill in returns.

Also calledtax return software for accountantsSA100 software for agents

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Online deadline: 31 January
Returns: SA100, SA800, SA900
Data pre-fill: 18-month client permission

How Self Assessment software works for practices

Agents can file the main SA100 and most supplementary pages through HM Revenue and Customs's online services, but partnership and trust returns and larger client books go through commercial software. HM Revenue and Customs's list of Self Assessment software suppliers, updated in October 2026, marks each product as for agents, individuals or both, and the forms it supports. Some software pulls client data from HM Revenue and Customs, such as PAYE income, pensions and taxable benefits: that needs the client's authorisation and an HM Revenue and Customs online services for agents account registered for Self Assessment for Agents, and the permission lasts 18 months. For 2025 to 2026, paper returns were due by 31 October 2026, and online returns and payment are due by 31 January 2027. Making Tax Digital for Income Tax started on 6 April 2026 for sole traders and landlords with income over £50,000, and a Self Assessment return is still needed for the year before each client joins. IRIS Keytime was discontinued on 31 March 2026, and IRIS points its users to IRIS Elements Tax.

Common questions

How much is Self Assessment software for accountants?+

TaxCalc's practice plans start at £187 a year plus VAT for 12 individual returns and £204 for individual and partnership returns. Capium charges £20 a month plus VAT for up to 100 clients, and Ftax for Agents starts at £11 plus VAT.

Can accountants file Self Assessment returns without software?+

Yes, for the SA100 and most supplementary pages, through HM Revenue and Customs's online services for agents. Partnership and trust returns, and practices with many clients, use commercial software.

Can the software fill in client data from HMRC?+

Some products can pull PAYE income, pensions, taxable benefits and other data. The client must authorise it, the practice needs an HM Revenue and Customs online services for agents account registered for Self Assessment for Agents, and the permission lasts 18 months.

Does MTD for Income Tax replace Self Assessment software?+

Not straight away. From 6 April 2026 clients with income over £50,000 send quarterly updates, but a Self Assessment return is still due for the year before they join, and exempt clients carry on filing returns.