The short answer: In a residency audit the state asserts you were a resident, and you have to prove otherwise. The single strongest piece of evidence is a contemporaneous day-by-day log of where you were, kept as the year happened and corroborated by independent records like phone location, card transactions, and travel data. Memory, calendars filled in later, and receipts alone rarely carry the day.
High-tax states audit residency because the money is large and the cases are winnable for them. When someone claims they moved from a high-tax state to a no-tax one, the old state has every incentive to test it, and it starts from the position that you owe. Your job is to dismantle that position with records. The ones that work share a single quality: they were created as events happened, not afterward.
The two questions an auditor asks
Almost every residency audit comes down to two things:
- Where were you, day by day? This is the day count against a threshold like New York’s 184 days, or the “where you spend your time” factor in states with no bright line.
- Where is the center of your life? Home, family, work, and the near-and-dear items that reveal where you actually live.
The second question is answered with documents about your life. The first is answered with a daily record, and it is the one most people cannot produce well after the fact.
The burden is on you
This is the part that surprises people. In a residency audit you are not presumed innocent. When the state claims you spent enough days there, you generally have to prove the days you were somewhere else. A day you cannot account for tends to be resolved in the state’s favor. With a threshold like 184 days, a handful of unproven days can be the difference between nonresident and resident, and between owing nothing and owing tax on your entire worldwide income.
A calendar you assemble the month the audit notice arrives has a predictable problem: it was assembled the month the audit notice arrived. Auditors know the difference between a record kept in real time and a story told in hindsight, and they weight them accordingly.
The evidence that holds up
The strongest defense is layered: a daily log at the center, with independent sources that corroborate it. No single source is complete, which is why they are used together.
- A contemporaneous day log. One clear answer for where you were each day, recorded as the year happened.
- Cell phone location data. Often the most granular and objective record of movement.
- Credit and debit card transactions. Time-and-place stamps, useful on days you spent money.
- Toll and transit records. E-ZPass and similar systems document interstate travel days precisely.
- Travel itineraries and boarding passes. Anchor the days you flew.
- Building access and swipe records. Key-fob logs at an office or building, where available.
- Utility and cell usage patterns. Show which home is genuinely lived in.
Build the record before you need it.
DayStayed keeps the contemporaneous daily log at the center of a strong audit defense, resolving each day automatically and exporting an audit-ready report with the methodology and signal trail behind every day.
How days get counted against you
Two rules recur across states and quietly inflate day counts. First, any part of a day in the state usually counts as a full day. A late-night arrival or an early-morning departure is a full day in most states. Second, days accumulate across the whole year and every trip, not just one visit. People routinely underestimate their total because a weekend here and a business trip there never felt like much until they were added up.
Some states carve out narrow exceptions, such as travel solely to pass through, or days in the state only for medical treatment, but you cannot rely on an exception you cannot document. The safest posture is to count every day and keep the proof.
An audit-ready recordkeeping checklist
- Keep a day-by-day log continuously, not starting when a notice arrives.
- Treat any part of a day in the high-tax state as a full day.
- Preserve phone location history, card statements, and toll records for the year.
- Save travel itineraries and boarding passes.
- Document the center-of-life factors: home, family, work, licenses, registrations, accounts.
- Keep records for several years back, since audits reach into prior years.
- Be able to produce a clean, dated export on request.