About FileSDLTonline: SDLT return software
FileSDLTonline is built by Truetax Systems Limited, which makes tax software for accountants, landlords and property businesses.
Why we built it
Most SDLT filing tools are modules inside large case-management systems, sold as part of a much bigger package. That suits some conveyancing firms. It doesn't suit accountancy practices filing for property-investor clients, property companies, or conveyancers who just want something fast and clear.
FileSDLTonline does one job: the Stamp Duty Land Tax return. It's built directly on HMRC's published technical specifications — the SDLT schema, business rules and Transaction Engine protocol — so returns are checked properly before they are sent.
What we believe
- The tax should be shown band by band, so anyone can check it.
- Errors should be caught before HMRC catches them.
- You should never pay for a rejected return.
- Credentials and client data deserve proper security.
SDLT schema version every return is validated against
Effective dates covered by the rate tables
Days to file — tracked for every case
England and Northern Ireland only, by design
How we check our figures
FileSDLTonline is built and run by Truetax Systems Limited, a UK company that makes tax software for accountants, conveyancers, landlords and property businesses. Every stamp duty figure on this site — in the calculator, the reports and the guides — comes from the same calculation engine used to file returns with HMRC.
- Tested against official examples. The engine is checked by an automated test suite of more than 300 tests, including HMRC's published SDLT examples, the Welsh Revenue Authority's LTT examples and Revenue Scotland's LBTT examples. The tests run whenever anything changes.
- Rates are data, dated by law. Each set of rates is stored with the date it took effect, so a purchase is always calculated with the rates in force on its effective date — including transitional rules after a rate rise.
- Built on HMRC's specifications. Returns are built against HMRC's SDLT schema (version 6.3) and checked against its business rules before they are sent.
How our guides are written
Our stamp duty guides summarise HMRC's published guidance in plain English. Each guide lists the GOV.UK pages it is based on, shows the date it was last reviewed, and uses worked examples calculated by the engine. Guides are reviewed when rates or rules change, such as at each Budget. They are general guidance, not legal or tax advice for a particular purchase.
Spotted something that looks wrong? Tell us and we will check it against HMRC's guidance and correct it.