Medical, Exempt & Military Days: Official Rules by Jurisdiction

Most day-count rules let you subtract days you were stuck somewhere for a medical emergency, days you held a specific exempt status, and, for the military, days served on active duty under orders. Under the US Substantial Presence Test, days you couldn't leave because of a medical condition that arose while in the US don't count, and certain people (students, diplomats, some teachers) are "exempt individuals" whose days never count at all. The exact mechanics differ by jurisdiction, so the rule that saves you depends on which clock you're trying to beat.

These exceptions matter because residency usually turns on a hard day threshold, 183 weighted days for the IRS, a fixed count in most US states, day bands in the UK Statutory Residence Test. A handful of subtracted days can be the difference between resident and nonresident. Below is how the three big categories, medical, exempt-status, and military, actually work, jurisdiction by jurisdiction.

The IRS medical condition exception

Under the SPT, you do not count any day you intended to leave the United States but could not because of a medical condition that arose while you were here. The key word is arose: the condition has to develop during your US stay. If you flew in specifically for treatment of a pre-existing problem, those days generally still count.

• The condition must have begun while you were present in the US, not before you arrived.
• You must have intended to leave on a normal schedule and been physically unable to.
• Days are excluded only for the period you genuinely couldn't travel, once you're cleared to fly, the clock restarts.
• You claim the exclusion on Form 8843, attaching a physician's statement describing the condition and the dates.

The medical exclusion stacks with the SPT's other carve-outs: days you commute from Canada or Mexico for work, days in transit between two foreign points (under 24 hours), and days as a crew member of a foreign vessel. Run the remaining days through the SPT calculator to see whether the subtractions drop you under 183 weighted days.

Exempt-individual days (the bigger lever)

"Exempt individual" is the most powerful US carve-out and the most misunderstood. It does not mean exempt from tax, it means your days don't count toward the SPT at all, so you file as a nonresident. Four groups qualify, each with its own clock:

Each exempt status has conditions, the teacher rule, for example, looks back over the prior six years and can be lost if you've been a student or teacher too recently. You report exempt status on Form 8843 even in years you have no US income. For the full student timeline, see our walkthrough of the F-1 to OPT to H-1B transition.

Military days: federal and state

Active-duty service members get protections that civilians don't, but they live mostly at the state level, not the federal SPT. The federal residency tests still apply to where in the world you're taxed; the military rules govern which US state can tax a service member who's stationed away from home.

Under the Servicemembers Civil Relief Act (SCRA), a service member doesn't lose or change their state of legal residence (domicile) just because military orders move them to another state. Days spent in a duty station under orders generally don't make that state your domicile. The Military Spouses Residency Relief Act extends similar protection to spouses, who can typically keep the service member's domicile for tax purposes.

• Federal SPT: US active-duty days are normal US days, there is no military exclusion from the substantial presence count itself.
• State domicile: orders-driven presence in a new state generally doesn't create domicile there under SCRA.
• Statutory residency: some states still apply a day-count "statutory resident" test; check whether military days are carved out before assuming you're safe.
• Spouses: can usually elect to match the service member's domicile, keeping a single home state for both.

If you're a service member juggling a home state like Florida with a duty station elsewhere, the practical task is proving your days abroad or out-of-state were under orders, which is exactly the kind of contemporaneous record an automatic day counter is built to keep.

How US states treat medical and exempt days

States that use a 183-day statutory-residency test don't all follow the IRS playbook on medical days, the rules are state-specific and often stricter. New York is the most cited example: it counts any part of a day you're physically present as a full day, with a narrow exception for days you were in the state solely to receive medical treatment for yourself or a family member in a hospital or similar facility.

That carve-out is deliberately tight. A day you were in New York for treatment but also stopped by the office, or stayed at your apartment rather than the hospital, can fail the test. Other states have their own day-counting quirks, some count midnights, some count any presence, so a medical day that's excluded in one state may be fully counted in another. When a state line is close, check the specific rule, not the federal one.

The UK and other day-count systems

Outside the US, the closest analogue is the UK's exceptional circumstances rule. Under the Statutory Residence Test, you can disregard days you were in the UK at the end of the day because of circumstances beyond your control, serious illness, a sudden family emergency, or events like a national emergency that prevented you from leaving. The relief is capped at 60 days per tax year, and HMRC applies it narrowly: you must have intended to leave and been genuinely prevented.

• UK SRT: up to 60 disregarded days a year for exceptional circumstances; run the rest through the 183-day calculator.
• Schengen: the 90/180 rule has no medical exclusion, an overstay is an overstay, so use the Schengen calculator to stay clear.
• Many other countries: apply a flat 183-day test with no medical carve-out at all, meaning a hospital stay still counts as presence.

The takeaway across every system: exceptions exist, but they're specific and evidence-driven. Keep dated records and supporting documents, a physician's letter, deployment orders, proof you were prevented from leaving, and apply the right jurisdiction's rule rather than assuming the IRS version travels. Tax Days lets you flag exempt, medical, and orders days so your defensible count is the one that shows up when the threshold gets close.