Tax Residency Audit: What Authorities Check and How to Prepare

March 19, 20267 min read

In a residency audit, tax authorities want to know exactly where you were on every day of the year. They verify this using passport stamps, flight records, credit card transactions, cell phone carrier data, toll records, and social media activity. The burden of proof is on you. If you cannot document your days, the auditor will fill the gaps using their own data, and their assumptions will not be in your favor.

Quick summary: HMRC recommends keeping a daily diary noting your location at midnight. The IRS requires documentation for the Physical Presence Test but does not prescribe specific records. New York State auditors routinely subpoena cell phone carrier records and credit card statements. Keep records for at least 7 years. Contemporaneous records (created at the time) carry more weight than reconstructions from memory.

What triggers a residency audit?

Audits are not random. They are usually triggered by something specific:

You filed taxes in a new state or country claiming non-residence in the old one
Your claimed residency does not match your financial activity (bank transactions, credit card usage in the "wrong" location)
You claimed the Foreign Earned Income Exclusion or a treaty benefit
A data-sharing agreement (CRS, FATCA) flagged an inconsistency between your declared residency and your financial accounts
You crossed a high-tax/low-tax boundary (New York to Florida, UK to UAE, Germany to Portugal)

According to HBK CPA, the most common trigger is a change of residency to a lower-tax jurisdiction. High-tax states and countries are motivated to challenge the change and keep you on their tax rolls.

What do tax authorities check in an audit?

Passport stamps and travel records

The most basic evidence. Entry and exit stamps show when you crossed borders. But stamps are not always reliable: automated e-gates often do not produce stamps, and Schengen internal borders have no passport control. Supplement stamps with flight itineraries, boarding passes, and hotel bookings.

Credit card and bank statements

Auditors look at where your transactions occur. According to Anchin CPA, state auditors scrutinize credit card transactions, checking account statements, and debit card usage to establish your physical location. A credit card swipe in Manhattan on a day you claimed to be in Miami is the kind of evidence that shifts an audit against you.

Cell phone carrier records

This is where audits get invasive. According to the CPA Journal (2017), New York State auditors routinely subpoena cell phone records directly from carriers. They separate voice and data transmissions chronologically to establish your location day by day.

One important caveat: cell tower pings can be inaccurate near state or country borders. The Monaeo blog documented cases where cell tower data placed people in the wrong state. If you live near a border, this data can work against you even when you were on the right side of the line.

Auditors increasingly check public social media posts, check-ins, and geotagged photos. A post from a New York restaurant on a day you claimed to be in Florida is evidence.

Other records

According to HBK CPA and the NYS nonresident audit guidelines, auditors also request:

E-ZPass and toll records
Gym and club membership swipe records
Doctor and dentist appointment records
Lease agreements and utility bills
Voter registration and driver's license location
School records for children

The pattern is clear: auditors reconstruct your daily location using every digital trace you leave. Any day without your own documentation is a day the auditor documents for you.

HMRC is the most explicit tax authority about record-keeping. The RDR3 guidance for the UK Statutory Residence Test recommends:

A diary of where you are each day, specifically noting whether you were in the UK at midnight
Records of hours spent working in the UK and overseas on each day
Travel documents including boarding passes and passport stamps
Evidence of accommodation arrangements and how properties are used
Documentation of family ties

The midnight rule makes HMRC's requirements precise. A day counts only if you are in the UK at midnight. Your diary should record this specific fact.

What does the IRS require?

The IRS is less prescriptive. Publication 519 (2025) requires documentation for the Physical Presence Test (330 days abroad in a 12-month period for the FEIE), but does not list specific acceptable records.

In practice, the IRS accepts: passport stamps, flight records, boarding passes, hotel receipts, rental agreements, and a contemporaneous travel log. Form 8843 is required to claim the exempt individual exclusion from the Substantial Presence Test.

The most important IRS-related guidance: weak travel documentation is the primary reason FEIE exclusions are denied in audits, according to BrightTax. If you claim the FEIE, your day-by-day records need to prove 330 days of foreign presence without gaps.

How long should I keep records?

At least 7 years. Tax authorities can audit several years back:

The IRS generally has 3 years from filing to audit, but 6 years if income was underreported by more than 25%, and no limit for fraud
HMRC can go back 4 years for simple errors, 6 for careless errors, 20 for deliberate errors
US state tax authorities typically have 3-4 year windows, but some extend longer

Keep records for the longest applicable period. 7 years covers most scenarios.

What makes documentation "audit-ready"?

Three qualities matter:

Contemporaneous. Created at the time, not reconstructed later. A travel log maintained daily is stronger than a spreadsheet you built from memory in March for the prior year. Auditors know the difference.

Consistent. Your records should tell the same story. If your passport shows you entered France on March 3, your credit card should show a French transaction around that date, and your travel log should list France for that period. Inconsistencies raise questions.

Complete. Every day should be accounted for. Gaps are where auditors make assumptions. If your records cover 300 days and leave 65 blank, the auditor may place you in the jurisdiction that generates the most tax revenue for those 65 days.

How does a day tracker help with audits?

A day tracker does two things that matter in an audit:

First, it maintains a contemporaneous record. Every trip you log is timestamped. Over time, this creates a complete daily location history that you can export when needed.

Second, it does the math correctly. The rolling windows, weighted formulas, and fiscal year boundaries that make manual tracking error-prone are handled by the software. An export from a tracker that applies the correct rules is more credible than a spreadsheet with formulas an auditor has to verify.

I built Jetseen with audit-readiness as a core feature. CSV exports filtered by date range. PDF reports with dates, countries, purposes, and entry documents. Records your tax advisor can use directly without reformatting.

Whatever tool you use, the key is starting now. You cannot go back and create records for days you did not document at the time.

FAQ

Can tax authorities really check my cell phone records? Yes. New York State auditors routinely subpoena carrier records, according to the CPA Journal. Other states and countries have similar powers, though the practice is most aggressive in high-tax US states.

Are passport stamps enough to prove my days? They are accepted evidence but not always sufficient. Many border crossings no longer produce stamps (Schengen internal borders, automated e-gates). Supplement with flight records, boarding passes, and a daily location log.

What if I do not have records for past years? Reconstruct what you can from flight bookings, credit card statements, and email confirmations. A reconstructed record is better than nothing but weaker than a contemporaneous log. Going forward, start maintaining records now.

How detailed do my records need to be? Account for every day. Note your country and city. For UK purposes, note whether you were present at midnight. For US purposes, any part of a day counts. The more specific your records, the stronger your position.