How to complete a UK Tax Return (SA100) as a non-resident

If you no longer live in the UK, you may still have to file a tax return with HMRC.

When you are a UK resident and you only derive income from the UK completing a tax return can be relatively straight forward - although this can have some complexity if you are a Director or have Capital gains/losses to report.

The tax rules for non-residents tend to be different, and as a non-resident you will have to complete supplemental forms. Non-residents are also likely to receive non-UK based income from employment, capital gains and other sources, which requires additional reporting. Non-UK residents are also likely to be subject to the tax rules of another jurisdiction which could mean there are tax treaties to take into consideration.

All of these additional requirements make completing a tax return as a non-resident much more taxing (excuse the pun) than for UK residents who have no international mobility complexities to add into the mix.

This article looks at the basics around Self Assessment Tax Returns and the additional details and forms non-residents will likely need to take into consideration.

What is a Self-Assessment tax return?

A Self-Assessment tax return is a declaration of the income you have received during a tax year. For example, the 2023/24 self-assessment tax return will cover the tax year ending 5 April 2024. Note the tax year begins on 6 April and ends on 5 April.

The tax return will enable HMRC to calculate how much tax you owe in the UK, or any rebates which are owed to you, from income you received during the tax year under review.

Under normal circumstances, if HMRC deems that you are required to complete a Self-Assessment tax return, they will send you a notification once the tax year has ended which will full due to be submitted by October 31^st (by paper) that year, or by January 31^st of the following year if submitted online.

Any tax payments will be due by 31^st January. You may also need to make a payment on account on 31 July.

Example: You are requested to submit a tax return for the tax year 2023/24. You receive a notification in the post in May 2023. Your tax return will be due by October 31^st 2024, if you intend to complete your tax return by post. If you are filing your tax return online, it must be submitted by 31^st January 2025 and all tax payments due to HMRC must also be received within this same deadline.

What you will need to file a UK tax return if you are a non-resident

Unique Taxpayer Reference (UTR) number. This is a reference number provided by HMRC that you will need if you're required to complete a tax return. If someone is completing your tax return on your behalf they will need this number. Our partners can assist you obtaining this number if that help is required.
National Insurance (NI) number.
SA100 Tax Return Form. This is the tax return form itself.
SA109 Form. This is a supplemental tax form is needed by non-residents to determine their tax residency status in the UK and is needed if you have income coming from the UK (rental, employment or dividends). It is also used to determine domicile status. The SA109 form should be submitted at the same time as your tax return.
P60 form which details income which UK tax has already been paid on.
Details of any untaxed income from the relevant tax year.
Self-employed people will need to include details about any expenses incurred.
Charity or pensions contributions - which would be eligible for tax relief.

You may also need any of the following supplementary forms:

SA106 Form. This form is only used if you need to declare any foreign income and/or gains on your tax return.
SA107 Form. This form is used only if you received income from any trusts, settlements or from someone's estate after their death.
SA108 Form. This is used to report any UK Capital gains or Capital losses.

Filling in your SA100 tax return form

The SA100 form is broken into four sections:

Income - taxed and untaxed
Pensions contributions
Charity Contributions
Benefits received

You will need to declare all income and contributions in the relevant boxes.

If income has been derived as a company director (for example dividends), property, self employment, capital gains or foreign earned income you will need to complete one or more supplementary form(s).

Do I have to submit a UK tax return if I live abroad?

Just because you no longer live in the UK, you may still be required to complete a tax return. If you are deemed to be a non-UK resident, it may still be necessary to complete a tax return if you have UK sourced income, even if you owe no tax.

Typical scenarios that may require a tax return for non-residents to be completed include:

If you are a director of a UK company
If you receive profits from a UK partnership
If you earn an income in the UK through self-employment
If you do not live in the UK, but you do some or all of your work in the UK
If you are in receipt of UK rental income
If you make capital gains from the sale or disposal of assets in the UK

Income received from investments (e.g. interest and dividends) might still need to be declared even if they are your UK-only income. This area can be complex, so it is always worth getting advice before deciding on whether to declare the income or not.

If you work in the UK, unless tax has already been deducted by your employer through the pay as you earn scheme, any work you do will be taxable and you will therefore be required to complete a tax return.

It is also important to remember that you may have to be taxed on your income in your country of residence if it is not in the UK. The UK does, however, have double taxation treaties with some countries which will mean that tax is only payable in one country.

How to work out if you are a UK tax resident

As has been already explained, whether you are a UK tax resident or not will determine what you need to include in your tax return, including the forms you need to complete. As a rule, you will generally not be considered a tax resident of the UK if you have not been present in the UK for 183 or more in any tax year.

However, in 2013 the UK government introduced the Statutory Residence Test which introduced additional criteria which is used to establish your UK tax residence status, which includes looking at the various ties that you have with the UK.

It is vital that you correctly interpret the Statutory Residence Test to establish your UK residence status and we have produced a guide to working out whether you are a UK tax resident or not, as well as an easy to follow flow chart. But if you are in any doubt or need assistance, you should request an introduction to one of our UK tax specialists.

Penalties for filing your tax return after the 31st January deadline

If you file or pay your Self-Assessment after the 31^st January you will incur a penalty. The penalty regime currently in place is as follows:

1 day late: Initial penalty of £100
3 Months late: Automatic penalty of £10 per day up to a maximum of £900
6 months late: A further penalty of the greater of £300 or 5% of the tax that would have been due and payable if the Return had been submitted on time.
12 months late: Another penalty of £300 or 5% of the tax that would have been due and payable if the Return had been submitted on time.

In addition to the above you will be required to pay tax-geared penalties and interest on any outstanding tax payments.

Can I complete my tax return online as a non-resident?

If you are non-resident, you will only be able to complete your tax return online if you have special software that enables it. This is because the supplemental forms that are required by non-residents, specifically the SA109 form, cannot be submitted using HMRC systems directly. UK tax specialists will, however, have access to the software needed to file online.

I’m not British, but I live in the UK - do I need to file a tax return?

If you are a foreign national living in the UK, deemed to be of non-UK domicile but UK resident, with UK income and foreign income and/or gains too, from overseas, then your Self-Assessment tax return will need to include information on:

your UK income
your capital gains realized on assets in the UK, and
your foreign income and capital gains, form overseas, and whether you bring it to the UK or not.

A number of key factors will determine whether you should complete a tax return, as well as the supplemental forms required, and you should always seek professional advice to avoid any penalties or double taxation.

What are the most common mistakes to avoid?

Thinking you can submit your SA100 online with the SA109

The most common mistake is for a non-resident to think you can complete your tax return online when your submission must be supported by filing a hard copy of the supplementary return "SA109 - Residence, remittance basis etc." Failure to do so, HMRC will have no record of your non-resident status causing complications as they will assume you remain taxable in the UK on your worldwide income and gains on an arising basis.

Misunderstanding when CGT is due (or at least reported) if you don't live in the UK

If you are selling a UK assets, such as a residential property, you are likely to need to at least report the sale of the assets, even if no tax is due.

Incorrect interpretation of the Statutory Residence Test

While it's quite simple to determine that you are a tax resident of the UK, simply by spending time in the UK, ensuring you are not a tax resident is dependent on more factors. Failure to correctly interpret the Statutory Residence Test correctly can result in an incorrect determination of your UK tax residence.

Incorrectly applying any double tax treaties

Some people incorrectly assume that because tax has been paid in one particular jurisdiction, no tax is due in the UK. This may or not be the case, but correctly interpreting the complex tax treaties is key to knowing what you will only have to pay tax on in one jurisdiction and the correct way to report taxes to avoid double tax.

When to request help with your tax returns

If you have international complexities relating to your tax return, such as you are a non-resident or you have foreign earned income, you should always seek assistance before submitting to ensure that all the information and calculations are submitted correctly. This includes the completion of supplemental forms and correct implementation of tax relief available through double tax treaties.

Attempting to complete a tax return on your own is possible and the Government website contains a series of guides, manuals and examples to assist you, however it can be incredibly stressful, and if you get it wrong you might end up paying fines and interest on any late payments.

Through Experts for Expats you can speak to a trusted UK tax specialist who will be able to assist you with your UK tax return, no matter where you live. If you make your request before 15th January 2025, our partner should be able to review your case and complete your tax return before the 31st January deadline.

Once you have been connected with one of our partners, you will be invited to book a free discovery call to discuss your situation and help you establish whether you need help with your tax return.

Following your discovery call they will be able to determine which forms you need, any potential surprises you may not have considered and provide you with a proposal and fee breakdown for completing your tax return on your behalf.

Speak to a UK tax specialist