Knowing the rule is only half the job. When a tax authority or a border officer doubts your day count, you are usually the one who has to prove it.
The same question, asked in reverse
Most of what we write here is about counting — the Schengen 90/180 rule, the 183-day tax tests, the physical-presence thresholds for residence and citizenship. But counting assumes you already know the dates. The harder moment comes later, when someone official asks you to demonstrate them — and disagrees with your figure.
That is the burden of proof, and across both tax and immigration it tends to rest on the individual, not the authority. The exact rules vary by country, but the pattern is consistent: the state records that you were somewhere, and asks you to account for the rest.
In tax, you usually carry it
When a residence position is challenged, the taxpayer is generally the one who has to make the case. In the UK, in a tax appeal it is normally the taxpayer who bears the burden of proof, to the civil standard of the balance of probabilities — more likely than not, rather than beyond reasonable doubt (Low Incomes Tax Reform Group). If you claim you were non-resident, you are the one who must show it.
The US is built the same way. Even if you trip the Substantial Presence Test, you may be able to step back out of US tax residence through the closer-connection exception — but only if you file for it. The IRS is explicit: "You must file Form 8840, Closer Connection Exception Statement for Aliens, to claim the Closer Connection Exception." And if you miss the deadline, you "cannot claim the closer connection exception to the substantial presence test, unless you can show by clear and convincing evidence that you took reasonable actions to become aware of the filing requirements" (IRS). The relief is real, but it is yours to claim and yours to substantiate.
Immigration asks the same of you
Applications for a residence permit, settlement or citizenship turn on days present and days absent — and the applicant, again, carries the proof. US naturalisation is a clear example: the applicant bears the burden of establishing eligibility by a preponderance of the evidence — that it is "more likely than not" they meet every requirement, including the continuous-residence and physical-presence rules (USCIS Policy Manual). Many countries make you list every trip abroad over a multi-year window to evidence exactly that, which is its own paperwork trap.
A particular danger sits inside this. An authority that knows two dates — an entry and a later exit — can reasonably presume you were present for everything in between unless you can show otherwise. A gap you cannot account for is rarely treated as neutral; it is often counted against you.
Stamps were never a ledger
The traditional proof was a passport stamp. It was always a poor one — date-only, frequently illegible, and never a running total — and it is now disappearing. The EU's Entry/Exit System changes the picture on both sides. As the European Commission states, "as of 10 April 2026, the EES replaces the stamping of passports," and the system instead "registers the person's name, travel document data, biometric data ... and the date and place of entry and exit" (European Commission).
Two consequences follow. The authorities now hold a precise, automatic record of your external border crossings — see our guide to EES. And you lose the stamp you might once have pointed to. If the official record and your memory disagree, the one holding a contemporaneous log is in the stronger position.
What actually counts as evidence
No single document proves a day; a consistent body of them does. The records people fall back on, depending on the question, include:
- travel tickets and boarding passes showing each entry and exit;
- accommodation, tenancy or hotel records placing you somewhere on a date;
- card and bank transactions that quietly timestamp your location;
- employer, payroll or assignment records;
- and your own contemporaneous diary of where you were each day.
The common thread is that this evidence is most credible when it was created at the time, not reconstructed afterwards for a form. Authorities know the difference between a record kept as you went and a best-effort guess assembled under deadline.
Where Countly fits
You cannot control which authority asks, or how strict the standard is. You can control whether, when the question comes, you have an answer already written down. The single most useful thing to hold is a contemporaneous, day-by-day record of which country you were in and when you crossed each border — exactly the raw material every test, and every challenge to it, runs on.
That is the quiet job Countly does. It keeps an automatic, private, on-device log of your days per country and your border crossings — no account, nothing leaving your phone — and watches your Schengen 90/180 balance, tax-residency thresholds and visa limits against it. When a tax authority, an immigration officer or your own accountant asks how many days, you are reading from a record you kept as it happened, not rebuilding one from memory. For the mechanics of doing this well, see how to count your days abroad.
The burden may be yours. A clean record is how you carry it lightly.
General information only — not legal or tax advice. Burden-of-proof rules, residence tests and immigration requirements are country-specific and change; check the current official guidance or a qualified adviser for your situation.