A Canadian who runs a US LLC and travels to the US asks one question every winter: "How many days can I spend before the IRS treats me as a US resident?" The Substantial Presence Test (SPT) is the rule. The IRS publishes the formula. The accounting firms publish summaries. What is missing is the practical thing: a scenario matrix showing what happens with realistic travel patterns, plus a clear decision tree on whether you file Form 8840 or Form 8833 to maintain Canadian residency. This post is that gap.
30-second answer
A Canadian becomes a US tax resident under SPT if their weighted day count over a 3-year rolling window reaches 183 days. The formula counts current-year days fully, prior-year days at one-third, and 2-years-prior days at one-sixth. If you exceed the threshold, you can still maintain Canadian residency by filing Form 8840 (Closer Connection Exception, only if current-year days under 183) or Form 8833 (treaty tie-breaker, regardless of day count) before the deadline. Day counts only matter for federal residency. State-level rules can be stricter.
The SPT formula
Three numbers, one threshold.
| Year | Weight | Calculation |
|---|---|---|
| Current year | × 1 | Days physically present in the US |
| Prior year | × 1/3 | Days physically present in the US in the prior calendar year |
| 2 years prior | × 1/6 | Days physically present in the US 2 calendar years ago |
You also need at least 31 days in the current year for the test to apply at all. Sum the three weighted numbers. If the sum reaches 183, you meet SPT and are a US tax resident for the current year, taxed on worldwide income unless you file an exception or treaty position.
A "day" is any day where you were physically in the US for any portion. Half-day trips count as full days. Days with very limited presence (medical emergency, transit while in airport, certain commuting) can be excluded.
Scenario matrix by travel pattern
Most Canadian LLC owners do not have unusual schedules, but the same total days can play out differently depending on how they distribute over 3 years.
| Pattern | Year -2 days | Year -1 days | Current days | Weighted total | SPT triggered? |
|---|---|---|---|---|---|
| Heavy current year | 0 | 0 | 200 | 200 | Yes |
| Even split, modest | 100 | 100 | 100 | 100 + 33 + 17 = 150 | No |
| Even split, heavier | 130 | 130 | 130 | 130 + 43 + 22 = 195 | Yes |
| Snowbird, growing | 90 | 110 | 130 | 130 + 37 + 15 = 182 | No (just under) |
| Snowbird, threshold | 120 | 120 | 120 | 120 + 40 + 20 = 180 | No |
| Year-1 spike, current low | 60 | 200 | 80 | 80 + 67 + 10 = 157 | No |
| First-year US trip | 0 | 0 | 130 | 130 | No |
| First-year heavy | 0 | 0 | 183 | 183 | Yes |
Two takeaways. First, 121 days every year for 3 consecutive years stays under the threshold (121 + 40 + 20 = 181). This is the practical "safe" number for predictable travel. Second, a single heavy year over 200 days triggers SPT regardless of prior history. The 3-year average forgives spikes if the 2 prior years were light.
Form 8840 vs Form 8833: which one and when
Two separate forms cover two different situations. Confusing them is one of the most common cross-border filing mistakes.
| Form | Use when | What it claims |
|---|---|---|
| Form 8840 (Closer Connection Exception) | Current-year days are 122-182 (you triggered SPT but stayed under 183 in current year) | You have a closer connection to Canada based on facts and circumstances. US treats you as non-resident |
| Form 8833 (Treaty-Based Position) | Any case, including current-year days at 183 or more | You invoke the Canada-US treaty tie-breaker rule (Article IV) to be treated as a Canadian resident |
The decision tree:
- Is your current-year US presence under 31 days? If yes, SPT does not apply. No form needed.
- Is your weighted 3-year total under 183? If yes, SPT does not apply. No form needed.
- Is your weighted total at 183 or more, but current-year days are under 183? Form 8840 is available if you can establish a closer connection to Canada (facts: tax home, family, vehicle, voting registration, drivers license, banking).
- Are your current-year days at 183 or more, or do you fail the closer-connection facts? Form 8833 is your only path. The treaty tie-breaker analyzes permanent home, center of vital interests, habitual abode, citizenship.
Both forms have filing deadlines. Form 8840 must be filed by June 15 of the year following the tax year (or with Form 1040-NR if filing one). Form 8833 is filed with Form 1040-NR. Missing the deadline means losing the exception and being treated as a US resident by default.
Treaty tie-breaker (Article IV)
When both Canada and the US claim you as a tax resident, the Canada-US treaty Article IV applies a tie-breaker test in this order:
- Permanent home: Where do you have a permanent home available? If only one country, you are resident of that country.
- Center of vital interests: If permanent homes in both, where are your personal and economic ties stronger (family, work, business, social)?
- Habitual abode: If center of vital interests is unclear, where do you spend more time on a habitual basis?
- Citizenship: If habitual abode is in both or neither, your citizenship decides. Canadian citizens are tied to Canada.
Most cross-border Canadian LLC owners win the tie-breaker on permanent home or center of vital interests. The Article IV mechanic is invoked via Form 8833 attached to Form 1040-NR.
Snowbird scenario: Canadian winter in the US
Many Canadian LLC owners spend winters in the US (Florida, Arizona, California). A 4-month winter stay every year tests the SPT.
| Pattern | Days/year | Year -2 | Year -1 | Current | Weighted | SPT? |
|---|---|---|---|---|---|---|
| Florida 3 months | 90 | 90 | 90 | 90 | 90 + 30 + 15 = 135 | No |
| Florida 4 months | 121 | 121 | 121 | 121 | 121 + 40 + 20 = 181 | No |
| Florida 4.5 months | 135 | 135 | 135 | 135 | 135 + 45 + 23 = 203 | Yes |
| Arizona winter + summer biz trips | 130 | 130 | 130 | 130 | 130 + 43 + 22 = 195 | Yes |
| Florida 6 months | 180 | 180 | 180 | 180 | 180 + 60 + 30 = 270 | Yes |
Snowbirds at 121 days/year stay safe. Above 122/year for 3+ consecutive years, SPT is met and Form 8840 must be filed annually. The 6-month winter pattern almost always triggers SPT and may fail Form 8840's closer connection facts (depending on driver's license, voter registration, primary banking).
US visa types and SPT
Different visas affect day counting.
| Visa | Days counted toward SPT? |
|---|---|
| Visitor (B-1/B-2) | Yes, every day counted |
| Business (E-2 investor) | Yes, every day counted |
| L-1 (intracompany transfer) | Yes |
| Student (F-1) | Excluded for first 5 calendar years |
| Diplomat (A or G) | Excluded |
| Teacher/trainee (J or Q) | Excluded for first 2 years |
| Commuter from Canada | Excluded if you regularly commute to work and return same day |
Most Canadian LLC owners enter on B-1/B-2 and have every day counted. The commuter exception is narrow and applies only to true daily-return cross-border workers (Windsor-Detroit, Niagara Falls, etc.).
State-level residency
Federal SPT is one analysis. State residency can be stricter.
| State | Day-based residency rule |
|---|---|
| California | Domicile-based, days are evidence but not the only test |
| New York | 183+ days + permanent place of abode = statutory resident |
| Florida | No state income tax |
| Texas | No state income tax |
| Arizona | 9-month presence + intent = resident |
A Canadian LLC owner who maintains California ties but spends under 183 days could still be deemed a California resident under domicile rules. Filing Form 8840 federally does not waive state residency.
Worked examples
Case 1: Toronto SaaS founder, occasional US visits
90 days/year for the past 3 years (conferences, customer visits).
| Item | Result |
|---|---|
| Weighted total | 90 + 30 + 15 = 135 |
| SPT met? | No |
| Form needed? | None |
| Risk | Low |
Case 2: Vancouver consultant, mid-level travel
130 days each of past 3 years (extended client engagements).
| Item | Result |
|---|---|
| Weighted total | 130 + 43 + 22 = 195 |
| SPT met? | Yes (over 183) |
| Current-year days | 130 (under 183 threshold for Form 8840) |
| Path | Form 8840 (Closer Connection); must establish Canadian closer connection facts |
| Risk | Medium. Document Canadian tax home, vehicle, family, banking |
Case 3: Calgary developer with Florida winter
Florida 4.5 months (135 days) every winter. No business trips.
| Item | Result |
|---|---|
| Weighted total | 135 + 45 + 23 = 203 |
| SPT met? | Yes |
| Current-year days | 135 (under 183) |
| Path | Form 8840 if closer connection facts hold |
| Risk | Medium-high. Watch state residency in FL or migration to AZ where domicile rules tighter |
Case 4: Edmonton founder with E-2 visa, US office full-time
180 days current, 200 days prior, 220 days 2 years prior.
| Item | Result |
|---|---|
| Weighted total | 180 + 67 + 37 = 284 |
| SPT met? | Yes |
| Current-year days | 180 (under 183) |
| Path | Form 8840 likely fails (E-2 + US office = US is center of vital interests) |
| Alternative | Form 8833 treaty tie-breaker, but Article IV likely picks US as residence |
| Outcome | Probably US tax resident, file Form 1040 (not 1040-NR) |
Frequently asked questions
My Canadian LLC has a US trade or business but I personally only spend 60 days/year in the US. Do I owe US personal tax?
No, not under SPT. 60 days fall well below the threshold. You file Form 1040-NR for the LLC's effectively connected income, but you remain a Canadian tax resident on personal worldwide income.
I forgot to file Form 8840 last year and spent over 183 days weighted. What now?
Late-filed Form 8840 can be accepted with reasonable cause explanation. The IRS published guidance allows late filing in good faith situations. File as soon as possible with a statement explaining the delay. If denied, Form 8833 treaty tie-breaker remains an option.
Does a US driver's license disqualify me from Form 8840 closer connection?
It is one factor, not automatic disqualification. The IRS evaluates the totality of facts. Holding a US driver's license while keeping Canadian provincial license, primary banking in Canada, family in Canada, and tax filing in Canada generally still supports closer connection. Cross-border CPAs typically advise against acquiring US licenses for non-essential purposes.