When do I need to submit my first self-assessment tax return?

First, you need to know which tax year you started trading in. For example, if you started trading on July 1^st 2025, that falls into the tax year April 6^th 2025 to April 5^th 2026. Your tax return will be due by January 31^st of the following year, so in this example you’d need to submit your tax return by January 31^st 2027.

Do I have to use accounting software, or will a spreadsheet do?