How tax authorities cross-check your data (and yours with the airlines')

There’s an old myth among expats: “if I don’t register as a resident, they can’t catch me”.

Tax authorities don’t need your cooperation. They already have these data sources.

1. PNR — Your reservations, on a plate

The EU PNR (Passenger Name Record) system has been live since 2018. Every airline is legally required to transmit to authorities:

• Your name, date of birth, contact info
• Full flight itinerary (origin, destination, dates)
• Payment method, seat, baggage
• Booking details (when, where, which agency)

This data is kept for 5 years and routinely cross-shared between EU authorities. Your tax office gets PNR every time you fly, including intra-EU flights.

The takeaway: the tax office knows when you enter and leave the country — without you lifting a finger.

2. CRS — Your bank account, on a plate

The OECD Common Reporting Standard (CRS) (2017) compels over 100 countries to automatically swap banking data. If you have an account abroad, that bank reports:

• Year-end balances, interest, dividends
• Account holder info: name, declared residence, tax ID
• Linked accounts

Your home country gets this data every year. If you declare residency in Cyprus but the Spanish tax office sees you receiving dividends in a Cyprus account in your name… they cross it against your Form 720 declaration (mandatory for Spanish residents with €50,000+ in foreign assets).

3. The paradox that creates most cases

What catches most people isn’t the PNR or the CRS. It’s this:

You file taxes yourself.

Registered as a Spanish self-employed “just in case” while claiming Cypriot residency? You’re already on the radar. Your spouse files as a Spanish resident and your kids attend Spanish schools? Presumption of Spanish residency.

The tax office combines data like this:

PNR → real days in country
CRS → wealth abroad
Form 720 → declared foreign assets
Form 100 → income tax filed
Social Security → contribution dates
Census registration → declared address

If the six don’t reconcile, they open a procedure.

A typical case

María lives 200 days in Cyprus. Works remotely for a Spanish company. Gets paid in a Cyprus account. Files in Cyprus.

The Spanish tax office sees:

• PNR: María entered Spain 3 times in 2024, totalling 95 days. Not a resident by days.
• CRS: María holds €180,000 in Cyprus accounts, declared in Cyprus.
• Form 720: María didn’t file Form 720 → fine on its own.
• Employer: the Spanish company kept withholding Spanish income tax from her salary by administrative error.

The tax office sends a request. María has to prove:

1. Her 95 days in Spain (PNR matches → no dispute)
2. That she wasn’t there longer on days when the tax office has no PNR (non-EU connections, intra-Schengen trips without PNR)

How does she prove the days the PNR doesn’t capture? Boarding passes, stamps, receipts, hotel bookings.

María had a manual spreadsheet missing the summer. The tax office assumed she was in Spain → bumped to 180 days → “presumption of residency” → 12 months of litigation.

The detail almost nobody knows

PNR only covers commercial flights with origin/destination in EU/Schengen airports. It doesn’t cover:

• Private flights
• Intra-EU train trips
• Cruises
• Extra-Schengen flights without an EU stopover
• Cross-border car/ferry trips

So if you took the Eurostar from Paris to London, the tax office doesn’t have that data. But the auditor who sees a hole in your PNR expects you to fill it in. The ball is back in your court.

What you can control

You can’t stop the data crossing. But you can have the complete version of your history while they have the partial one.

The boarding passes already in your inbox cover 100% of your commercial flights — and once you add Eurostars, ferries, and overnight buses, your record is more detailed than the authority’s PNR file.

DayProof ingests all of that automatically from your email. When the request lands, you’ll have a PDF more complete than their dossier.

Free during beta.