How to file a Self Assessment return online for free
You do not need paid software to send a Self Assessment return. HMRC’s own service on GOV.UK is free, and it is the route this site will always point to first. Software can still be useful for bookkeeping, but it is optional. This guide walks through the official registration and filing pages in our own words, including who cannot use the free online service and what to have ready before you sign in.
First, check whether you must file, then register
Before you create an account in a hurry, confirm that you need to send a return. The official “who must send a tax return” page and the “check if you need a tax return” tool are the right starting points, and our who needs to file guide summarises the published list. If HMRC has already asked you to file, you must do so even if you think the tax is nil.
You must tell HMRC by 5 October if you need to complete a return for the previous year and you have either not sent a return before, or you registered before but did not need to send a return for 2024/25. You tell HMRC by registering for Self Assessment. The official registration page for this season says you must tell HMRC by 5 October 2026 for the tax year that ended on 5 April 2026. If you tell them after that date you could get a penalty. If you have already registered and are waiting for a Unique Taxpayer Reference, that page also points you to where you can check when to expect a reply.
If you have registered before but did not send a return last year, you may need to reactivate your Self Assessment account. The official service will explain how to do that. Filing without reactivating an existing account, the filing page warns, may delay the return. Agents who file for clients have a separate official route; this guide is written for people filing for themselves.
What the free online service does
You can file your Self Assessment tax return online if you are self-employed, or if you are not self-employed but you still send a return — for example because you receive income from renting out a property. You can file any time on or after 6 April following the end of the tax year, and you must send it by the deadline or you will get a penalty. For the year most readers are completing now, that online deadline is 23:59 on 31 January 2027, with a 30 December 2026 date if you want to pay through a tax code, as set out in the deadlines guide.
The official service also lets you view returns you have made before, check your details, check how much you owe, print your tax calculation, and sign up for paperless notifications. You do not have to complete the return in one go; you can save your entry and go back later. You will need to sign in, or create sign-in details, and you will need your Unique Taxpayer Reference. You may be asked to prove your identity, usually with photo ID such as a passport or driving licence.
There are official limits. You cannot use this service to file a return online for a partnership, for a trust or for an estate, if you lived abroad as a non-resident, to report multiple chargeable event gains, or if you get income from a trust, are a Lloyd’s underwriter or a religious minister. In those cases HMRC tells you to use commercial software or to download or request other forms. If you are sending an SA100 for 2020/21 or earlier, official guidance points you to forms at the National Archives rather than the current online service.
Where software fits, and where it does not
Commercial software can import bookkeeping, store invoices, or file for some of the groups the free service does not support. It is not required for a straightforward sole-trader or property return that the official service accepts. If you do use software, you are still sending a return to HMRC, and the deadlines and penalties are the same. This site may later include sponsored links to official software homepages, clearly marked; those links are optional, and they are not a substitute for the free GOV.UK filing service. Until any affiliate programme approves this site, those homepages carry no tracking identifier.
A planning estimate from our tax calculator is useful for setting money aside, but the figure that matters is the calculation the official service (or approved software) produces from the return you actually submit. Keep the records that support each box: bank statements, invoices, mileage, and any P60 or other employment documents. HMRC’s overview page reminds you that you need records to fill the return in correctly, and that you may have to pay interest and a penalty if you do not file and pay on time.
After you submit
Pay the bill by the official payment date, which for most people is 23:59 on 31 January 2027 for the 2025/26 year, and check whether payments on account towards the next year are due as well. If you need to reduce those instalments, do it through the official account or form SA303, as described in the payments on account guide. If something in the calculation looks wrong, use HMRC’s own amendment process rather than hoping a third-party estimate will correct it. AssessTally cannot file for you, cannot see your return, and is not affiliated with HMRC.
Paper returns, paying the bill, and identity checks
A paper SA100 is still available: you can download it or call HMRC and ask for the form. For this filing season the paper deadline of 23:59 on 31 October 2026 has already passed, so a paper return sent now is late on that track. The online service remains open until 23:59 on 31 January 2027 for most individual returns. If you started a paper form and have not posted it, switching to the official online service is usually the faster way to get a return in before the January date.
Filing and paying are related but not identical tasks. The official overview says HMRC will calculate what you owe based on what you report, and that you should pay your Self Assessment bill by 31 January. The payment options HMRC offers — including paying through a tax code if you submitted in time, or paying by the methods shown in your account — sit on the official payment pages. Do not wait for a paper bill if your online calculation already shows an amount due.
Identity checks exist to keep the service safe. If you are asked for a passport or driving licence and you cannot complete the check on the first try, leave time to try again before 31 January. The same is true if you cannot find your Unique Taxpayer Reference: recover it through the official routes rather than guessing, and do not leave that recovery until the evening of the deadline.