UK tax if you're Spanish and self-employed in the UK: a plain-English guide

Moving from Spain to the UK and working for yourself is exciting. Understanding the tax implications — in a second language, in a system you have never used before — is considerably less so.

This guide is for Spanish nationals living and working in the UK as self-employed individuals. It covers what you owe in the UK, what your obligations in Spain might still be, and how the two countries’ tax systems interact.

Are you UK tax resident?

The starting point for everything is your UK tax residency status, which is determined by the Statutory Residence Test (SRT). The SRT is a set of rules that considers how many days you spend in the UK, your ties to the country (family, property, work), and whether you have left the UK in recent years.

As a broad guide:

• If you spend 183 days or more in the UK in a tax year, you are automatically UK resident for that year
• If you spend fewer than 16 days in the UK, you are automatically non-resident
• Between those thresholds, the answer depends on your specific ties and circumstances

If you have moved to the UK to live and work, you are almost certainly UK tax resident. That matters because UK residents pay UK tax on their worldwide income — not just income earned in the UK.

What do you need to declare in the UK?

If you are self-employed in the UK, you must register with HMRC and file a Self Assessment tax return each year. You need to declare:

• Your self-employment income and allowable expenses
• Any other UK income (rental income, savings interest, dividends)
• Any foreign income — including income from Spain — if you are UK resident

The UK tax year runs from 6 April to 5 April the following year. Your Self Assessment deadline is 31 January after the end of the tax year.

The personal allowance

Everyone resident in the UK is entitled to a personal allowance — an amount of income you can earn before paying any UK tax. For 2025/26, this is £12,570. Income above this is taxed at the basic rate (20%), higher rate (40%), or additional rate (45%) depending on the total.

National Insurance

As a self-employed person, you also pay National Insurance contributions on your profits above the small profits threshold. Class 4 NICs are currently charged at 9% on profits between £12,570 and £50,270, and 2% above that.

Do you still have obligations in Spain?

This depends on whether you are also considered Spanish tax resident.

Spain determines tax residency using its own rules. As a general principle, if you spend more than 183 days per year in Spain, or if Spain is your main economic base, you are considered Spanish tax resident. If you have genuinely moved to the UK — your home is here, your work is here, your family is here — you are likely no longer Spanish tax resident for the period you are in the UK.

However, there are important nuances:

• The year you move is often a split year for both countries
• You may have retained economic ties to Spain (a property, investments, a pension) that affect your status
• If you are uncertain, the answer is to get advice rather than assume

If you are not Spanish tax resident, you may still have obligations to declare Spanish-source income (such as rental income from a Spanish property) to the Spanish tax authorities as a non-resident, via the Modelo 210.

The Double Taxation Treaty

The UK and Spain have a Double Taxation Treaty that prevents the same income being taxed in full by both countries. In practice, this means:

• You pay tax on your income in the country where it arises (or where you are resident, depending on the type of income)
• You claim credit for tax already paid in the other country when declaring it elsewhere
• You do not simply pay twice — but the paperwork needs to be done correctly on both sides

The treaty is not automatic relief. It requires active management, correct categorisation of income types, and the right declarations in both countries.

What about the Modelo 720?

The Modelo 720 is a Spanish obligation to disclose overseas assets exceeding €50,000 in aggregate. It applies to Spanish tax residents. If you are genuinely UK resident and no longer Spanish tax resident, the Modelo 720 does not apply to your UK assets.

If you are in a grey area on residency, or if you were recently Spanish resident, this is something to take specific advice on. The penalties for non-compliance are significant.

The most common mistakes

In our experience working with Spanish self-employed clients in the UK, the most common issues are:

Assuming UK PAYE covers everything. If you also have self-employment income, rental income, or Spanish income alongside employment, you still need to file a Self Assessment even if you pay PAYE tax on your salary.

Not declaring Spanish income on the UK return. UK residents must declare worldwide income. Spanish rental income, dividends from a Spanish company, and Spanish bank interest all need to go on the UK Self Assessment.

Missing the registration deadline. You must register for Self Assessment by 5 October after the end of the tax year in which you first became self-employed. Miss this and you may face penalties.

Assuming residency is straightforward. The year you move is rarely clean-cut. Both countries have specific rules for split-year treatment that need to be applied correctly.

Getting it right

If you are Spanish, self-employed in the UK, and unsure whether your tax affairs are in order — the straightforward answer is to speak to an accountant who understands both systems.

At ABL Accounts, we work with Spanish-speaking clients across the UK. We handle your UK Self Assessment, advise on your obligations in Spain, and apply the Double Taxation Treaty correctly. And we do all of it in whichever language is easier for you.

Book a free consultation — in English or en español.