Third automatic UK test: full-time work in the UK

Q: Can I trigger the third automatic UK test if I live abroad?

Yes. The test has no residency or home requirement. A person who lives in Dublin but physically works in the UK four days a week will trigger AUT3 if the 75% threshold is met and no significant break from UK work exists. Where you sleep or where your home is makes no difference to this test.

Q: What is the 75% threshold for AUT3?

The 75% threshold means that UK working days — days on which you do more than 3 hours of work in the UK — must represent at least 75% of your total working days (days on which you do more than 3 hours of work in any location) over the 365-day reference period.

Most people think about UK tax residency in terms of days, how many nights they slept in the UK. The third automatic UK test works differently. It looks at where you physically worked, not where you lived. If at least 75% of your working days over a 365-day period are days on which you did more than 3 hours of work in the UK, the test makes you automatically UK resident, regardless of where you live, where your employer is based, or how many nights you spent in the UK.

This catches a specific group that most SRT guidance ignores: cross-border workers. A management consultant who flies from Brussels to London four days a week. A contractor who is nominally based in Dublin but does almost all of their project work at a UK client site. A senior manager who relocated to Germany but still runs the UK operation in person. All of these people may trigger the third automatic UK test without realising it.

The test is the mirror of the third automatic overseas test. They are two sides of the same coin, designed to be mutually exclusive. Understanding one requires understanding how they differ from each other.

To check whether this test applies to your situation, the SRT questionnaire works through all six automatic tests in the correct order and produces a clear determination in about 10 minutes.

Key points

The third automatic UK test is about where you physically work, not where you live or who employs you
You meet the test if at least 75% of your working days over a valid 365-day reference period are UK working days
A "UK working day" is any day you do more than 3 hours of work physically in the UK, employer location is irrelevant
The 365-day period must have no significant break from UK work (no 31+ consecutive days with no UK working days)
The test is the mirror of the third automatic overseas test, they cannot both apply to the same person in the same reference period
Split year Case 1 may apply if AUT3 is what makes you UK resident from mid-year

What the third automatic UK test requires

The third automatic UK test is set out at paragraph 15 of Schedule 45 to the Finance Act 2013 and explained at RFIG20370. All four of the following conditions must be met:

There is a period of 365 consecutive days ("the reference period"), all or part of which falls within the tax year.
During that reference period, the individual does not have a significant break from UK work, meaning no 31 or more consecutive days pass in which no day is a UK working day (RFIG22210).
The number of days in the reference period on which the individual does more than 3 hours of work in the UK is at least 75% of the total days on which they work more than 3 hours in any location.
At least one UK working day in the reference period falls within the tax year being assessed.

All four conditions must be satisfied simultaneously.

The 365-day reference period

The reference period is any consecutive 365-day window, it does not have to align with the tax year or start on 6 April. It can straddle the 5 April/6 April boundary. What matters is that at least part of it falls in the tax year being assessed and that a valid period (meeting Conditions 2 and 3) can be identified.

In practice, HMRC will identify the most favourable 365-day period available. If any valid reference period can be found, the test is engaged.

The significant break condition

A significant break from UK work (RFIG22210) means 31 or more consecutive days during which no day is a UK working day. This is not simply 31 days of annual leave, it is 31 consecutive days with no day on which you worked more than 3 hours in the UK.

What breaks the reference period:

An extended overseas posting lasting 31+ days with no return to UK work
A career break or sabbatical of 31+ days with no UK working days
A period of sick leave long enough that no UK work is performed for 31+ days

What does not break the reference period:

A 3-week summer holiday (21 days, under 31)
Two weeks working entirely from overseas followed by immediate return to UK work
A bank holiday weekend with no working

The 75% UK working day test

To calculate whether the 75% threshold is met:

Count the total days in the reference period on which you did more than 3 hours of work in any location ("total working days")
Count the days on which you did more than 3 hours of work physically in the UK ("UK working days")
Divide UK working days by total working days
If the result is 0.75 or more, the condition is met

Example: you work 230 total working days in the reference period. Of those, 180 are UK working days. 180 / 230 = 78%. Condition 3 is met.

The 75% threshold means you can spend up to 25% of your working days outside the UK and still trigger the test. A person who works 4 UK days and 1 overseas day each week consistently will be above the threshold.

What counts as a UK working day (RFIG22040)

A UK working day is any day on which you do more than 3 hours of work physically in the UK. The location of your employer, the location of your client, and the governing law of your contract are all irrelevant. What matters is where you were physically present while performing the work.

This means:

A day working at your employer's London office = a UK working day
A day in client meetings in Manchester = a UK working day
A day working from a hotel room in Birmingham before catching an evening flight = a UK working day if more than 3 hours of work is done there

This also means:

A day working from home in France for a UK employer = not a UK working day
A day on a video call with UK colleagues from your Spanish flat = not a UK working day
A day at a client site in Dublin = not a UK working day

The 3-hour threshold must be met in the UK. A day on which you work 2 hours in the UK then 5 hours in France is not a UK working day, even though you worked more than 3 hours in total.

What counts as work?

Work for SRT purposes includes all activities performed in the course of employment or self-employment where the duties are substantive. Board attendance, client meetings, project delivery, and operational management all count. Commuting does not count as work. Incidental activities (brief emails, checking messages) generally do not count if they are not the substance of the duties.

Worked example: Marcus (full-time UK employee)

Marcus is British and lives in Leeds. He works for a UK financial services firm in a full-time employed role. His working pattern is standard: five days per week in the office, about 240 working days a year. He takes four weeks' annual leave, mostly in the UK with one two-week holiday in Spain.

AUT3 check for 2025-26:

Reference period: any 365-day window across the year works. Take 6 April 2025 to 5 April 2026.
Significant break: Marcus's longest period without UK working days is his two-week Spanish holiday, 14 days. Under 31. No significant break.
UK working day count: approximately 235 days of 5-days-a-week work, minus the overseas holiday days. Say 220 UK working days out of 225 total working days (he occasionally works from home in the UK on the non-holiday overseas days, but let us assume the Spanish days are not UK working days). 220 / 225 = 98%. Well above 75%.

Result: AUT3 is met. Marcus is automatically UK resident for 2025-26. This is the expected outcome, he lives and works in the UK. The calculation is shown here to demonstrate the mechanics.

Key lesson: for a straightforward UK employee, AUT3 is met without any close analysis. The test becomes interesting at the margins, cross-border workers and people who split their working time between the UK and overseas.

Worked example: Freya (cross-border commuter)

Freya is Irish and lives in Dublin. She is a management consultant employed by a UK consulting firm. Her working pattern throughout 2025-26 is to travel to London on Monday morning and return to Dublin on Thursday evening, working at the London office Monday through Thursday (4 days per week). On Fridays she works from home in Dublin.

She takes four weeks' annual leave during the year, spread across a mix of UK and non-UK periods. Her longest continuous stretch with no UK working days is a 3-week Christmas and New Year break, 21 days. She never has a gap of 31+ days without UK working days.

AUT3 check for 2025-26:

Reference period: any valid 365-day period within the year. Freya's pattern is consistent, so any 365-day window works.
Significant break: 21-day Christmas break is the longest gap. No significant break (under 31 days). Condition 2 satisfied.
UK working day count: approximately 4 out of every 5 working days are UK working days (Monday-Thursday in London; Friday in Dublin). Take the full reference period: say 220 total working days, of which 176 are UK working days (80%). 80% >= 75%. Condition 3 satisfied.
At least one UK working day falls in 2025-26. Condition 4 satisfied.

Result: AUT3 is met. Freya is automatically UK resident for 2025-26, despite living in Dublin, sleeping in Dublin four nights a week, and being Irish. The SRT does not care where she sleeps or where her home is. The third automatic UK test is purely about where she physically works.

What this means practically: Freya is UK resident under the SRT. She will also likely be Irish resident under Irish tax law (resident where she lives). She will need to rely on the UK-Ireland double tax treaty to determine where she ultimately pays tax on employment income. But her UK residency status under the SRT, and her self-assessment filing obligation, is settled by AUT3.

Key lesson: the third automatic UK test catches cross-border workers with no regard for where they sleep. If 75%+ of your working days are in the UK, the test applies.

AUT3 vs the third automatic overseas test

The third automatic UK test and the third automatic overseas test are mirrors of each other. They are designed to be mutually exclusive: a person who triggers one cannot trigger the other in the same reference period.

Feature	AUT3 (third automatic UK test)	AOT3 (third automatic overseas test)
Effect if met	Automatically UK resident	Automatically non-resident
Working day threshold	At least 75% of working days are UK working days	No more than 30 UK working days in the reference period
Significant break condition	No significant break from UK work (31+ days)	No significant break from overseas work (31+ days)
SRT stage	Stage 3, automatic UK test	Stage 2, automatic overseas test
Employer location	Irrelevant	Irrelevant

Because AOT3 is assessed before AUT3 in the SRT sequence (overseas tests come first), a person who passes AOT3 never reaches AUT3. And the thresholds make simultaneous application impossible: if you have no more than 30 UK working days, you cannot have 75%+ UK working days unless you barely work at all.

The practical implication: if you spend most of your working time in the UK, AOT3 will not rescue you. You need to reduce UK working days below 30 in any reference period, or ensure no valid 365-day period without a significant break from UK work can be constructed, to avoid AUT3.

Interaction with split year treatment

If AUT3 is what makes you UK resident in a tax year, Case 1 split year treatment may be available. Case 1 applies when an individual becomes UK resident in the tax year by starting full-time work in the UK. The "UK part" of the year runs from the date they started full-time UK work; the overseas part covers the period before that date.

This matters most for people who take up a UK work role mid-year. Without Case 1, they would be UK resident for the full tax year and potentially taxed on worldwide income arising throughout. With Case 1, only income arising in the UK part of the year is within the UK tax charge.

For a full account of when split year treatment applies and how the year is divided, split year treatment covers all eight cases.

Common questions

What is the third automatic UK test?

The third automatic UK test (RFIG20370) makes you automatically UK resident if four conditions are met over a 365-day reference period: there is a valid 365-day period all or part of which falls in the tax year; no significant break from UK work occurs (no 31+ consecutive days without a UK working day); at least 75% of your working days are UK working days; and at least one UK working day falls in the tax year.

Does working for a UK employer make me UK resident?

No. Employer location is irrelevant. What matters is where you physically perform your work. If you work remotely for a UK employer from France, your working days are French working days, not UK working days. The third automatic UK test is about physical location of work, not the nationality or location of the employer.

Can I trigger the third automatic UK test if I live abroad?

Yes. The test has no residency or home requirement. Freya in the example above lives in Dublin but triggers AUT3 because she physically works in the UK four days a week. Where you sleep or where your home is makes no difference to this test.

What counts as a UK working day?

A UK working day is any day on which you do more than 3 hours of work physically in the UK (RFIG22040). The work must be physically performed in the UK, work done on a video call from overseas for a UK employer does not count. The 3-hour threshold must be met in the UK alone.

What is the 75% threshold for AUT3?

The 75% threshold means that UK working days, days on which you do more than 3 hours of work in the UK, must represent at least 75% of your total working days (days on which you do more than 3 hours of work in any location) over the 365-day reference period.

What is a significant break from UK work?

A significant break from UK work (RFIG22210) is a period of 31 or more consecutive days during which no day is a UK working day. If such a break occurs within a potential reference period, that period cannot be used to trigger AUT3. The individual would need to identify a different 365-day period with no such break.

How does the third automatic UK test interact with the third automatic overseas test?

They are mutually exclusive. The third automatic overseas test (AOT3) requires no more than 30 UK working days in the reference period. AUT3 requires at least 75% of working days to be UK working days. A person cannot satisfy both thresholds simultaneously in the same reference period. If you pass AOT3 (making you automatically non-resident), you never reach the automatic UK tests.

What is the statutory basis for the third automatic UK test?

The test is set out at paragraph 15 of Schedule 45 to the Finance Act 2013. HMRC's explanation of the conditions is at RFIG20370, with supplementary guidance on time spent on UK work at RFIG20380, the definition of a UK working day at RFIG22040, and significant breaks from UK work at RFIG22210.

The third automatic UK test draws its line around where you work, not where you live. A cross-border commuter with four UK working days per week, a contractor working almost entirely on UK projects, a senior employee who runs UK operations in person, all of these people are at risk of triggering AUT3 regardless of where they sleep or who their employer is.

If your work takes you to the UK on most weeks, the SRT questionnaire will work through whether AUT3 applies to your situation. It covers all six automatic tests in the correct statutory order and produces a clear determination in about 10 minutes.

For context on how AUT3 sits alongside the five other automatic tests, how the six automatic tests work covers the full sequence.

This content is for informational purposes only and does not constitute tax advice. For complex situations, particularly cross-border employment, double tax treaty questions, or split year treatment, professional advice from a qualified tax adviser is recommended.