A tax residency tracker that counts every rule not just the days
Most day-counting apps give you a number. The number is the easy part. What decides an audit is whether you counted against the right threshold, over the right period, using the right definition of a "day", and whether you can prove it. Tax Days tracks all 50 US states, the federal Substantial Presence Test, Schengen 90/180, the UK Statutory Residence Test, and 200++ countries at once, on your iPhone, with the data staying there.
What you're up against
A spreadsheet cannot run a rolling window
Schengen 90/180 is not an annual budget, it is a window that moves every day. A spreadsheet that sums a column will tell you that you are fine right up until you are not.
Every jurisdiction defines a day differently
New York counts any part of a day. Utah generally counts the day only if you spent more time there than in any other state. Some countries require midnight presence. One day count cannot serve all of them.
Thresholds are not all 183
New York is 184, Oregon and Hawaii are 200, Idaho is 270, India and Malaysia are 182, Thailand is 180, and the US Substantial Presence Test weights three years together. Tracking against 183 everywhere is tracking against the wrong number almost everywhere.
Reconstructed records lose audits
A calendar rebuilt from card statements and photos after a notice arrives is worth far less than a log kept as you travelled. Contemporaneous is the word auditors use, and it means written at the time.
What Tax Days does for you
Counts your days against every jurisdiction you touch, simultaneously, each with its own threshold, period, and day-counting convention.
Warns you before you cross a line, not after, with the margin shown in days rather than a pass/fail.
Tracks automatically in the background on Pro, using significant-change monitoring rather than continuous GPS, and proposes trips for you to confirm.
Works entirely by hand if you prefer, with location turned off completely.
Keeps everything on your iPhone, with optional iCloud sync through Apple's CloudKit. There is no Tax Days server holding your location history.
Exports a contemporaneous day log you can hand to an accountant or an auditor.
The rules you actually need to track
US state statutory residence
All 50 states, including the 184-day traps in NY, NJ, MA, and CT and the higher thresholds in Oregon, Hawaii, and Idaho.
Read the guide →Substantial Presence Test
The IRS three-year weighted count, including exempt-individual windows for F-1 and J-1 visas.
Read the guide →Schengen 90/180
The rolling window, counted across all 29 Schengen states rather than per country.
Read the guide →UK Statutory Residence Test
Automatic overseas and UK tests plus the sufficient-ties test, over the 6 April to 5 April tax year.
Read the guide →The 183-day rule, everywhere else
The most common threshold in the world, with the per-country variations that matter across 200++ jurisdictions.
Read the guide →Treaty tie-breakers
When two countries both claim you, the OECD Article 4 sequence that decides which one wins.
Read the guide →
Free guides and tools
- Guide
What is tax residency?
The definition, the tests, and how the thresholds differ.
- Guide
Best tax residency tracker apps in 2026
Every app in the category, compared honestly.
- Guide
How Tax Days compares
Head-to-head against TaxBird, Domicile365, Monaeo, Daysium, and a spreadsheet.
- Guide
Spreadsheet vs app
Where a spreadsheet genuinely works, and where it breaks.
- Calculator
Which calculator do I need?
A short wizard that points you at the right rule.
- Calculator
Multi-country day counter
Count one itinerary against several jurisdictions at once.
Common questions
What is a tax residency tracker app?
An app that records where you were on each day and counts those days against the residency thresholds of every jurisdiction that could tax you. A good one handles the fact that thresholds, counting periods, and the definition of a 'day' all differ by jurisdiction, and produces a contemporaneous record you can rely on if you are audited.
How much does Tax Days cost?
$29.99 per year, with a free tier that covers a limited set of rules. That is the least expensive option in the category: TaxBird is $39.99/year, iReside $34.99/year, Domicile365 around $220/year, Monaeo $999/year, and Daysium starts at £950/year.
Do I have to let it track my location?
No. Automatic background tracking is available on Pro and uses battery-efficient significant-change monitoring rather than continuous GPS, processed on-device, proposing trips for you to confirm. You can also turn location off entirely and log every trip by hand. Either way the data stays on your iPhone.
Does the app work for US states and international rules together?
Yes, and that combination is the reason it exists. Most apps in this category specialise: US-only snowbird tracking, or enterprise mobility for HR teams. Tax Days runs all 50 US states, the federal Substantial Presence Test, Schengen 90/180, the UK SRT, and 200++ countries at the same time, so one trip is counted against every rule it touches.
Is there an Android version?
Not currently. Tax Days is an iPhone app, with a Mac build via Catalyst. If you are on Android, TaxBird is the credible cross-platform option for US-focused tracking.
Will the records hold up in an audit?
The app produces a contemporaneous day log, meaning entries created as you travel rather than reconstructed afterwards, which is the distinction auditors care about. It is a record-keeping tool, not tax advice: it tells you where you stood on the day count, and your accountant advises on what to do about it.
Know exactly where you stand
Track every jurisdiction you touch, get warned before you cross a threshold, and keep the record on your own phone.
