We get this question more than any other. Sometimes it is a joke. Sometimes it is not. It goes like this: “So I could just install Southbound, leave the phone with my wife in Naples, fly back to Westchester for the summer, and the app would show me in Florida all year, right?”
The honest answer is yes, the app would show the phone in Florida all year. And that would be the worst piece of evidence you ever created.
This post explains why, and why we built Southbound so that the answer stays no. It is not legal advice. It is a description of how residency evidence actually works, and how a day counter earns the right to be believed.
The app records a phone, not a person
Southbound tracks the location of the device it is installed on. That is the whole product. When location updates arrive, the app checks each position against the Florida state boundary and writes the day to a ledger with a timestamp, the number of location fixes, and a confidence score. At the end of the year you can export a report with daily evidence summaries and a fingerprint of selected ledger fields.
Notice what is not in that description: any claim about where you were. The app cannot know that. No app can. What it can do is produce a record of collected device-location checks and identified manual entries.
That distinction is the entire reason the record is worth anything.
What an auditor does with your record
If you have read our post on what New York residency auditors actually look at, you know the pattern. The state does not ask you where you were and write it down. It builds its own calendar first, from sources you do not control: carrier cell tower logs, EZ-Pass and toll records, credit and debit card transactions, airline manifests, doorman logs, medical appointments, even where your dog goes to the vet.
Then it compares that calendar to yours.
Now run the phone-left-behind scenario through that process. Your Southbound report says Florida every day from June through September. Your carrier’s tower logs say your number, the one on your account, in your name, was pinging towers in White Plains every one of those days. Your Amex says Westchester. Your EZ-Pass says the Tappan Zee, twice a week.
You did not create evidence of Florida days. You created a document that contradicts the state’s evidence in your own handwriting, and you handed it over. An auditor who finds one fabricated record stops treating the rest of your file as a good-faith account. The days you genuinely spent in Florida are now suspect too.
A gap in your record is a gap. A fabricated record is a finding.
Why we built it this way on purpose
A day counter that could be gamed would be useless, because the person reading it would have no reason to trust it. Every design decision in Southbound comes back to that.
One device, one Apple ID, one person. The record is bound to the phone you carry. It syncs to your personal iCloud account, and to nowhere else. We never see it.
Days with retained checks show their evidence. The report does not just say “Florida.” It says how many location fixes were recorded that day and when. A day with forty fixes across sixteen hours looks like a day someone lived. A day with two fixes at 3 a.m. from a nightstand looks like something else, and the report shows that difference plainly.
Corrected days are labeled. If you change a day by hand, the ledger flags it as self-reported. It never pretends a manual entry was a recorded one.
The ledger has a fingerprint. The report includes a fingerprint of selected ledger fields when the report was generated. It does not prove when entries were created or whether they were previously edited.
You attest to it. The report states that the device was your own, carried on your person, and used by you alone. That is a sentence you sign, in effect, every time you hand the report to your CPA. We wrote it in so that the document states its own limits. Auditors respect documents that do that. They do not respect documents that overclaim.
None of this makes Southbound a lie detector. It makes Southbound the kind of record that survives being checked. That is the only kind worth paying for.
The real question underneath: what about my spouse?
Most people who ask about leaving the phone are not planning fraud. They are asking a different question badly. The real question is: “My wife and I both want to reach 183 days. Do we both need this?”
Yes. Each of you needs your own phone, your own Apple ID, and your own copy of Southbound.
This is not a licensing trick. It is how residency works. Domicile is determined per person. A married couple can have different domiciles. New York has audited spouses separately and reached different conclusions for each. Your wife’s Florida days are her Florida days. They do not transfer, and a report from her phone is evidence about her, not you.
The good news is that the counting is the same, so the household conversation gets simple. Two phones, two Departure Budgets, one dinner-table number each: how many days can I still spend up north this year? A shared household view, where both budgets sit on one screen, is on our roadmap. The underlying records will stay separate, because they have to.
What to do instead
If you are tempted to leave the phone, it is usually because you are worried about the count. Here is what actually helps.
Carry the phone. That is the whole method. Southbound uses the phone’s significant-location system, so it does not run continuous GPS. Carry the phone and review the record for gaps.
Check the Departure Budget before you book. The dashboard shows one number: how many days you can still spend outside Florida this year. Look at it before you book the flight, not after.
Correct honestly. If a day recorded wrong, fix it, and let the report show that you fixed it. A ledger with a few flagged corrections is far more credible than one that looks too clean.
Keep the other evidence too. Southbound is one strong record. Pair it with the ones that already exist: cards, tolls, flights. When they all say the same thing, the audit is short.
Frequently asked
Can I leave my phone in Florida and travel to count the days? No. Southbound records where the phone was, not where you were. A state auditor cross-checks against carrier cell records, card transactions, flights, and tolls. A phone left behind creates a contradiction in your own evidence, which is worse than a gap.
Can my spouse and I share one Southbound? No. Each person who is tracking days needs their own phone, their own Apple ID, and their own copy of Southbound. The record belongs to one device and one person. A shared household view is on the roadmap.
Does Southbound prove Florida residency on its own? No single record does. Southbound is contemporaneous documentation that supports your own account and lines up with the records an auditor will pull independently. That alignment is what makes it useful.
Southbound is on the App Store. It counts the Florida days it recorded, with location evidence where checks were retained. That is less exciting than a shortcut, and it is the only version that works.
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Published Sep 1, 2026