On 13 August 2026, HMRC published Guidelines for Compliance (GfC19), which cover the tax and National Insurance treatment of short-term business visitors to the UK. What's notable about these guidelines is not that they change the law but that they represent a deliberate effort to help employers get compliance right.
Here are the key takeaways from HMRC’s guidance that employers should know about.
Tax can bite from day one
A common misconception is that short-term business visitors to the UK have no income tax liability in the UK because they continue paying tax in their home country. That is wrong. An overseas employee who spends a single day in the UK can be subject to UK income tax on the earnings attributable to that day. UK domestic rules or a double-taxation treaty may ultimately relieve that liability, but it does not remove it automatically.
Treaties are not identical
Double-tax treaties generally prevent employees from paying income tax on the same income twice. The UK has a double-tax treaty with more than 130 other countries and it is common that one applies to a business visitor to the UK.
HMRC’s guidance on common errors refers to failures to check the terms of the relevant treaty and that the employee meets its specific requirements. International tax treaties often follow similar guiding principles. One of those is that a host country may not have taxing rights over earnings where the employee does not spend more than 183 days in the UK. However, subtle differences in treaty wording can make all the difference. For example, some treaties will state different reference periods – i.e. a fiscal year or a rolling 12-month period. Some of the more historical treaties (such as UK/Greece) omit standard treaty provisions altogether. Assuming all treaties work the same way is a common and costly mistake.
Counting days for treaty purposes
When counting days for double-taxation treaty purposes, HMRC calls out failures to count all UK days as a common error leading to interest and penalty charges.
Any time spent in the UK counts as a day, however brief. HMRC confirms that this “includes working days, non-working days such as weekends, annual leave, or sick leave”. The only exception is transit: time spent in the UK between two non-UK locations is excluded, but only if the person is genuinely passing through.
Tax and social security don’t always align
Double-taxation treaties cover tax, not social security (in the UK, National Insurance contributions).
These are dealt with separately under social security agreements, which have their own rules, their own thresholds and their own exemption mechanisms. The UK has a much smaller network of social security agreements, and where those aren’t in point, the domestic rules of each jurisdiction need to be considered to work out where liabilities arise. This means that employers sending employees to or from a country without a social security agreement may find themselves paying contributions in two places with no credit available.
Why does it matter and what should employers do?
Employers are facing an increasingly complex compliance and regulatory environment.
As we wrote about here, EU and UK based employers should prepare for an incoming shake-up to social security coordination. Similarly, employers with operations in the EU need to find ways of complying with an increasingly fragmented and uneven transposition of the EU Pay Transparency Directive. This has a particular bearing on employers with mobile international workforces as employees working temporarily in an EU member state, or a different EU member state from their home raises complex questions about how their pay should be reported under the Directive.
Against this background, HMRC’s guidance on key tax concepts and common errors is helpful. This guidance indicates they know that the rules can be difficult to follow and would rather help employers to do something by way of compliance effort, instead of nothing at all. This shouldn’t be ignored – we think it is likely that HMRC have an eye towards these resources being used against employers in the event of future non-compliance, and the new guidance will make it more difficult for employers to argue that a compliance error in one of the highlighted areas was not a careless mistake.
Employers with overseas employees visiting or working in the UK, even occasionally, should use this guidance as a prompt to:
- Review HMRC’s common errors. Do any of these errors apply to your organisation? If they do, address them now. That process may identify broader and potentially more significant historic liabilities. HMRC’s approach to issuing penalties is summarised here. Unprompted disclosures of historic errors will usually be treated more leniently than disclosures prompted by an HMRC audit.
- Refine systems and internal processes. Could your business tell HMRC who was in the UK, when, and for how long? In multinational organisations, compliance across jurisdictions will require open channels of coordination and communication between teams. Organisations that have historically managed overseas working on an informal basis will struggle. Without refreshing their systems, they are likely to face greater risks of liabilities and sanctions in the new compliance and regulatory environment.
For more detail on business visitor rules and managing international mobility risks, listen to our podcast where we discuss top tips for managing global mobility issues.
