Start your return for free — you only pay when you're ready to submit. SubmitFox submits directly to HMRC.
Start filing →Filing your Self Assessment online is the fastest, most straightforward way to submit your tax return to HMRC. You don't need an accountant — and with the right tool, most people are done in under 20 minutes.
What You Need Before You Start
- Your Unique Taxpayer Reference (UTR) — 10-digit number from HMRC
- Your National Insurance number
- Details of all income sources for the tax year: employment, self-employment, rental income, dividends, savings interest
- Records of any allowable expenses you want to claim
- P60 or P45 from your employer (if employed)
If you haven't yet registered for Self Assessment, you need to do that first. Registration takes around 10 days as HMRC sends your UTR by post.
How to File Your Self Assessment with SubmitFox
Create your account
Sign up to SubmitFox. It's free to start — you only pay when you're ready to submit.
Enter your income details
SubmitFox guides you through each income source with plain-English questions. No tax jargon. Enter your employment income, self-employment profit, rental income, and anything else relevant to your situation.
Review your tax calculation
SubmitFox calculates your tax in real time. You can see exactly what you owe — and why — before submitting.
Submit directly to HMRC
When you're happy, submit with one click. SubmitFox sends your return directly to HMRC's systems. You receive instant confirmation and a submission reference number.
Who Needs to File a Self Assessment?
You must file a Self Assessment tax return if, in the last tax year, any of the following apply:
- You were self-employed and earned more than £1,000
- You earned more than £100,000 in total
- You had rental income from property
- You received dividends from shares
- You had untaxed income over £2,500
- You claimed Child Benefit and earned over £60,000
- You were a company director
What Happens After You Submit?
Once submitted, HMRC processes your return and confirms it has been received. You can view your tax calculation and payment reference in your HMRC online account. Any tax owed must be paid by 31 January — you can pay by bank transfer, debit card, or through your HMRC account.
Ready to file your Self Assessment?
Start your return for free — you only pay when you're ready to submit.
SubmitFox submits directly to HMRC. Simple questions, clear calculations, instant confirmation.
Common Questions
Yes — the majority of people with straightforward tax situations file themselves. If your income is from employment, self-employment, property, or investments, you can file directly using SubmitFox without any accounting knowledge.
The online deadline is 31 January following the end of the tax year. For the 2024/25 tax year (ending 5 April 2025), the deadline is 31 January 2026. Paper returns have an earlier deadline of 31 October.
HMRC charges an automatic £100 penalty for returns filed after 31 January, even if you owe no tax. Further penalties apply at 3 months, 6 months, and 12 months. Interest is also charged on late payments.
First, register for Self Assessment with HMRC if you haven't already done so. This takes about 10 days as HMRC posts your UTR number. Once you have your UTR, you can create a SubmitFox account and work through your return at your own pace.
Yes. You can amend a submitted Self Assessment return up to 12 months after the original 31 January deadline. If you realise you made a mistake, you can correct it through your HMRC online account or by filing an amended return.