How to File Your Self Assessment (SA100) Online for Free with WeFile

Self Assessment can feel daunting when you are faced with tax terminology, calculations and an important legal declaration. WeFile turns the supported parts of the SA100 process into a guided online journey, helping you enter your details, review the calculation and submit your return directly to HMRC.

Our Self Assessment feature is permanently free for supported returns. There is no filing fee, membership requirement or subscription needed for an original return or an amendment. This guide explains exactly what the feature does, who can currently use it and what happens from the moment you start a return to the moment HMRC responds.

Important: WeFile currently supports a clearly defined set of 2025–26 tax situations. It does not yet cover every SA100 supplementary page or every type of income and relief. Always check the current scope before relying on the service.

Self Assessment is HMRC’s system for collecting Income Tax from people whose tax is not fully dealt with through PAYE or other automatic deductions. The SA100 is the main tax return. Depending on a person’s circumstances, extra supplementary pages may also be required for matters such as self-employment, UK property, foreign income or capital gains.

A return records relevant income, tax already deducted and supported reliefs or adjustments for a particular tax year. HMRC uses that information to establish the taxpayer’s position. Filing a return is a legal responsibility: the person submitting it must make sure the information is complete and correct to the best of their knowledge.

WeFile provides software for preparing and transmitting supported SA100 returns. WeFile does not provide tax advice, decide what you should disclose or replace a qualified accountant or tax adviser where professional judgement is needed.

The feature is designed around clarity, cost and direct submission:

• Free filing: supported original returns and amendments cost £0, whether or not you have a WeFile membership.
• A guided journey: the return is broken into manageable steps rather than presenting an empty tax form.
• Automatic calculations: WeFile calculates the supported tax position from the information entered, ready for you to review.
• Your own HMRC credentials: submission uses your own Government Gateway user ID and password, not a shared WeFile account.
• Direct submission: after your declaration, the return is transmitted to HMRC’s live Self Assessment service.
• Live status information: the return page shows submission progress and the result received from HMRC.
• Useful documents: you can review and download the supported SA100 return and tax calculation documents.
• Amendment support: eligible submitted or completed returns can be amended while preserving a separate submission history.

Free does not mean reduced care. The workflow includes validation, a calculation review, a formal declaration and a confirmation step before submission.

As at 22 September 2026, WeFile’s Self Assessment service supports the 2025–26 tax year for individuals who were UK tax resident for the full tax year and whose circumstances fit the supported categories.

Current supported areas include:

• employment income where a PAYE reference is available;
• UK bank and building society interest;
• UK dividends;
• supported pension contribution and Gift Aid adjustments;
• receipt of Marriage Allowance from a spouse or civil partner; and
• Student Loan and Postgraduate Loan repayment calculations.

The eligibility questions are important. If an answer indicates that required information falls outside WeFile’s current coverage, the return is blocked from submission through WeFile. Your answers remain saved, but you will need other HMRC-compatible software or professional help to complete that return.

Because product coverage can expand, check the live Self Assessment feature and scope page for the latest supported list before starting.

WeFile does not currently support returns requiring the following income types, supplementary pages or specialist treatments:

• self-employment or the SA103 pages;
• partnership income or the SA104 pages;
• UK property income or the SA105 pages;
• foreign income or the SA106 pages;
• trust or estate income or the SA107 pages;
• capital gains or the SA108 pages;
• non-residence, split-year treatment, the remittance basis or non-UK domicile matters associated with SA109;
• private or State pension income;
• employment benefits in kind reported through P11D information;
• the High Income Child Benefit Charge;
• filing as an agent on behalf of a client;
• ministers of religion, Lloyd’s underwriters, life insurance gains, or employment-related shares and securities;
• unauthorised pension payments or lifetime allowance charges;
• Gift Aid carry-back or relief for gifts of shares or land to charity; and
• other income, reliefs or circumstances outside the questions presented in the wizard.

This boundary protects users from submitting a return that omits a required section. If any unsupported category applies, do not try to force the figures into a different field. Use software that covers the necessary pages or seek advice from a qualified accountant or tax adviser.

Gathering your records first makes the guided process much quicker. Depending on your supported circumstances, you may need:

• your Unique Taxpayer Reference (UTR), National Insurance number and contact details;
• your own 12-character Government Gateway user ID and password;
• P60 and, where relevant, P45 information for each employment;
• the employer PAYE reference shown on your employment records;
• details of UK bank and building society interest;
• dividend vouchers or statements showing UK dividends;
• records of supported pension contributions and Gift Aid donations;
• Marriage Allowance information, if you receive the allowance;
• Student Loan or Postgraduate Loan plan details and relevant deductions; and
• details of tax already deducted from the supported income you report.

Use final records rather than estimates wherever possible. Keep the evidence used to prepare your return with your tax records after filing.

1. Create or sign in to your WeFile account

Sign in and open the Self Assessment area. Self Assessment is available without buying a membership or paying a filing charge.

2. Add the taxpayer profile

Create or choose the taxpayer whose return you are preparing. One WeFile account can hold more than one taxpayer profile, helping a user keep separate records organised without combining their returns.

3. Start the 2025–26 return

Create an original return for the selected taxpayer and tax year. WeFile prevents duplicate live original returns for the same taxpayer and year.

4. Complete the eligibility questions

Answer the scope questions accurately. These determine whether WeFile can support the full return. An out-of-scope answer stops submission rather than allowing an incomplete filing.

5. Enter income and adjustment details

Work through the guided sections for personal details, employment income, UK interest, UK dividends and supported adjustments. The active step is saved as you move through the wizard, helping protect your progress.

6. Review the calculation and documents

Check the figures, the calculated tax position and the downloadable documents. Make sure every amount agrees with your source records and that no relevant income or relief is missing.

7. Read and confirm the declaration

The final declaration is a legal confirmation. WeFile presents an explicit confirmation dialog before anything is submitted. Opening or cancelling that dialog does not submit the return.

8. Enter your Government Gateway credentials and submit

Use your own 12-character Government Gateway user ID and password. Once you confirm, WeFile securely sends the return to HMRC and displays the submission progress.

9. Keep the submission result and documents

When HMRC responds, review the status and retain the return, calculation and submission reference with your records. If HMRC rejects the return, review the returned information before retrying.

WeFile’s calculation takes the supported income, deductions, allowances and loan rules entered in the wizard and derives the tax position for review. The calculation stage is there to help you identify mistakes before the legal declaration.

Before submitting, check at least the following:

• the taxpayer identity and tax year are correct;
• every employment and PAYE reference has been entered accurately;
• gross income and tax deducted match the source documents;
• interest and dividend totals include all supported accounts and holdings;
• pension and Gift Aid entries use the amounts requested by the wizard;
• the Student Loan or Postgraduate Loan plan is correct; and
• the final calculation is consistent with your understanding and records.

If the result is unexpected, stop and recheck the source figures. Software can validate structure and calculate from the information supplied, but it cannot know that an otherwise plausible number was entered in error.

Your Government Gateway credentials are sensitive. WeFile encrypts stored credentials and only decrypts them when needed for transmission to HMRC. Passwords are not revealed to administrators, API-key callers or users working through impersonated sessions.

The submission step is intentionally separate from ordinary saving. You must enter valid credentials, read the declaration and confirm the irreversible submission action. Cancelling the confirmation leaves the return unsubmitted.

Never share your Government Gateway password by email or support message. If you believe it has been exposed, update it through the appropriate HMRC service before filing.

After confirmation, WeFile sends the return to HMRC and shows the latest submission state on the return details page. Status updates appear live while HMRC processes the submission; there is no need to repeatedly refresh the page.

HMRC may accept the return, report that it was previously submitted, or reject it with information that needs attention. Processing can sometimes take longer than expected. If that happens, WeFile continues checking in the background and keeps the persisted attempt count visible.

A rejection is not the same as an accepted filing. Read the message carefully, correct the return or credentials where appropriate, and retry only when the return is eligible to be resubmitted.

An original return is the first return for a taxpayer and tax year. Once an eligible original return filed through WeFile has been submitted or completed, a writable user can create an amendment from the return or Self Assessment dashboard. The amendment keeps its own reference and submission history while preserving the relationship to the original.

WeFile also supports a direct amendment route for a taxpayer whose original return was filed outside WeFile. In that case, there is no local original return to link to, but the amendment is still tracked as an amendment for that taxpayer and year.

Only amend a return when the information genuinely needs correcting. Review the complete amended position, not just the changed figure, before making a fresh declaration and submission.

For most taxpayers filing online for the 2025–26 tax year, the filing deadline is 31 January 2027. Tax due is generally payable by the applicable HMRC payment deadline, which is often the same date for the balancing payment. Registration, notification and special-case deadlines can differ, so check current HMRC guidance for your circumstances rather than relying on a general summary.

Consider using a qualified accountant or tax adviser if you are unsure whether income is taxable, need an unsupported supplementary page, have overseas or residence issues, need to make a complex claim, are correcting an older return, or simply do not understand the calculation. Professional advice may also be appropriate when records are incomplete or HMRC has opened an enquiry.

WeFile is filing software, not a substitute for individual tax advice. The service should only be used where the complete return falls within the supported scope.

Is Self Assessment filing through WeFile really free?

Yes. Supported original SA100 returns and amendments are permanently free for every user. You do not need a WeFile membership and there is no Self Assessment filing fee.

Which tax year does WeFile currently support?

WeFile currently supports the 2025–26 tax year only. Check the live Self Assessment scope page for future coverage updates.

Can I use WeFile if I am self-employed or receive rental income?

Not currently. Self-employment and UK property income require supplementary pages that are outside WeFile’s present Self Assessment scope.

Do I need my own Government Gateway account?

Yes. You submit using your own 12-character Government Gateway user ID and password. WeFile does not submit ordinary user returns through a shared account.

Can I save the return and finish it later?

Yes. Your progress is saved as you work through the guided return, so you can leave and continue later before submission.

Can I file an amendment?

Yes. You can create an amendment for an eligible original return filed through WeFile, or use the direct amendment route where the original was filed elsewhere.

What happens if my circumstances are not supported?

WeFile blocks submission and preserves your answers. You will need other HMRC-compatible software or help from a qualified accountant or tax adviser.

Does WeFile give tax advice?

No. WeFile helps prepare, calculate and submit supported returns, but it does not provide personalised tax advice or decide how tax law applies to your individual circumstances.

For supported 2025–26 tax situations, WeFile provides a clear route from your records to an HMRC submission: complete the guided questions, review the calculation, confirm the legal declaration and track the response — all without a filing fee.

Review the current Self Assessment scope before you begin, then sign in or create an account to start your return.

This article is general information, not tax advice. Tax rules, deadlines and software coverage can change. Check current HMRC guidance and seek professional advice where needed.