{"id":553,"date":"2019-06-25T17:11:29","date_gmt":"2019-06-25T16:11:29","guid":{"rendered":"https:\/\/taxfix.com\/en-uk\/?p=553"},"modified":"2025-04-07T15:46:16","modified_gmt":"2025-04-07T14:46:16","slug":"what-is-the-sa100-form","status":"publish","type":"post","link":"https:\/\/taxfix.com\/en-uk\/self-assessment-basics\/what-is-the-sa100-form\/","title":{"rendered":"The SA100 form: how to use it to file your Self Assessment tax return"},"content":{"rendered":"\n

If you\u2019re submitting by post, the SA100 form is the main document you need to fill out when doing your Self Assessment tax return.<\/p>\n\n\n\n

You fill out the same information whether you file an online or a paper tax return, so it\u2019s completely up to you how you want to file. Just remember, the deadline to file and submit your tax return by post is October 31st following the end of the tax year.<\/p>\n\n\n\n

Take a look at the below dates if you’re filing online.<\/p>\n\n\n<\/div> \n\n

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Key dates in the current <\/span>2025\/26 tax year \ud83d\udc47<\/b><\/p>\n\n\n\n\n\n\n\n\n
Deadline<\/b><\/td>\nDate<\/b><\/td>\nYear<\/b><\/td>\n<\/tr>\n
Tax year starts<\/span><\/td>\n6th April<\/span><\/td>\n2025<\/span><\/td>\n<\/tr>\n
Tax year ends<\/span><\/td>\n5th April<\/span><\/td>\n2026<\/span><\/td>\n<\/tr>\n
Register for self assessment<\/span><\/td>\n5th October<\/span><\/td>\n2026<\/span><\/td>\n<\/tr>\n
Pay tax bill by PAYE salary<\/span><\/td>\n30th December<\/span><\/td>\n2026<\/span><\/td>\n<\/tr>\n
Self assessment deadline<\/span><\/td>\n31st January<\/span><\/td>\n2027<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n\n <\/div>\n<\/div> \n\n
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If you\u2019re not sure that you\u2019ll need to submit and file a Self Assessment, then check out this guide on who needs to file a tax return<\/a>.<\/p>\n\n\n\n

How do I fill the SA100 form?<\/h2>\n\n\n\n

You\u2019ll find all the documents you\u2019ll need to print and fill out on HMRC\u2019s website<\/a>. <\/p>\n\n\n\n

There, you\u2019ll be able to pick the year you want to file for. Once you choose what year you need, you can download the SA100 tax return form to your computer. <\/p>\n\n\n\n

Remember, if you want the form for the 2024\/2025 tax year, you click on 2025. If you want it for the tax year before that, you can choose 2024, and so on.<\/p>\n\n\n\n

If you want to fill in tax return forms published before 2019, you can find them on the National Archive<\/a>.<\/p>\n\n\n\n

Once you\u2019ve picked your year, all you have to do is:<\/p>\n\n\n\n