183 日ルール計算ツール
日数による居住地ルールを持つ、あらゆる国や米国の州で使えます。しきい値（183 が最も一般的、NY / NJ / MA / CT は 184、その他は地域により異なる）を設定し、課税年度の期間を指定すれば、あとは計算ツールが処理します。
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旅程
- 旅程 1
What the 183-day rule actually says
There is no single 183-day rule. There is one number that dozens of unrelated laws happen to share, and each of them defines the count, the period it is measured over, and the consequence differently. The number itself is arithmetic: half of a 365-day year is 182.5 days, so 183 is the smallest whole number of days that is more than half a year. Spend 183 days in one place and you cannot have spent longer anywhere else.
What the number does depends on which of two rules you are reading, and the two are routinely confused:
- Domestic residence tests. A country's own law treats presence for a set number of days inside its own tax year as making you a tax resident, which usually means it can tax your worldwide income and expects a return. This is the rule most people mean, and it is what the calculator above counts against.
- The treaty 183-day rule. Article 15 of the OECD Model Tax Convention, which most bilateral tax treaties are built on, exempts your employment income from tax in the country you are working in only when three conditions hold together: you are present there no more than 183 days in aggregate in the relevant twelve-month period, your employer is not a resident of that country, and your pay is not borne by a permanent establishment your employer has there. Failing any one of the three, not only the day count, hands the taxing right to the country you worked in. Older treaties often measure the 183 days over the fiscal year rather than a rolling twelve months, so read the treaty that actually applies to you.
The two rules are independent. Staying under 183 days in a treaty country can protect your salary while a different domestic test still makes you resident. Where two countries both claim you, the tie-breaker in Article 4 of the same model treaty runs in a fixed order: permanent home, then centre of vital interests, then habitual abode, then nationality, and if none of those settles it, agreement between the two tax authorities. Day counts are the evidence at almost every step.
If both countries have a claim on you, work through the treaty tie-breaker tool next.
Where the number is written down
Four of the most-searched versions of the rule, with the provision each one comes from. Read the wording rather than the number: "at least 183 days" and "more than 183 days" are one day apart, and that day is the whole question.
| Jurisdiction | What the provision says | Basis |
|---|---|---|
| United States | The substantial presence test: 31 days in the current year and 183 days on a three-year weighted count that takes the current year in full, one third of the prior year, and one sixth of the year before that. | 26 U.S.C. § 7701(b)(3) |
| United Kingdom | The first automatic UK test is met if you spend at least 183 days in the UK in the tax year, which runs 6 April to 5 April. A day generally counts if you are in the UK at the end of it. | Finance Act 2013, Schedule 45 |
| Canada | You are deemed resident for the whole year if you sojourned in Canada for periods totalling 183 days or more in the calendar year. Day 183 is enough on its own. | Income Tax Act, section 250(1) |
| New York | Statutory residency requires a permanent place of abode in the state and more than 183 days there in the taxable year, so day 184 is the one that makes you a resident. Any part of a day generally counts as a full day. | N.Y. Tax Law § 605(b)(1)(B) |
Most other jurisdictions are a variation on one of these four patterns: a bare day count, a day count paired with a home you keep available, a weighted count across several years, or a day count that is only one of several tests.
A worked example
Take a 183-day threshold measured over the 2026 calendar year, in a jurisdiction that counts arrival and departure days in full, which is the common case. Four trips:
| Trip | Dates | Days | Running total |
|---|---|---|---|
| 1 | 8 January to 14 February | 38 | 38 |
| 2 | 2 April to 30 June | 90 | 128 |
| 3 | 5 September to 20 October | 46 | 174 |
| 4 | 18 December to 31 December | 14 | 188 |
Every figure counts both end dates. Trip 1 is 38 days, not 37: 24 days in January (the 8th to the 31st) plus 14 in February. Dropping one day per trip is the most common arithmetic error there is, and across a year of frequent travel it hides a week or more.
Trip 4 decides the year. It begins at 174 days, so its ninth day, 26 December, is day 183. The threshold is met, and in most systems that makes the whole year a resident year, including income earned during the eight months spent elsewhere.
Leave on 25 December instead and the year closes at 182 days. One day of calendar separates the two outcomes, which is why the projected crossing date matters more than the running total: it gives you the date to be gone by, before you book the flight.
管轄地域別の 183 日ルール
ほとんどの国は税務上の居住地に 183 日ルールを用いますが、細部は異なります。簡単なリファレンスは次のとおりです：
- 183 日、暦年：ほとんどの国、ドイツ、スペイン、フランス、イタリア、メキシコ、シンガポール、日本、ポルトガル（12 か月ローリング）。
- 184 日 ＋ 住居：ニューヨーク、ニュージャージー、マサチューセッツ、コネチカット、ペンシルベニア。
- UK SRT（Statutory Residence Test）：英国の課税年度（4 月 6 日から 4 月 5 日）における、結びつきと連動した日数テスト。
- オーストラリア：オーストラリアの所得年度（7 月 1 日から 6 月 30 日）における 183 日。
- カナダ：居住上の結びつきテストと並行して適用される 183 日のみなし居住者ルール。
- UAE：居住ビザと住居がある場合は 90 日、一般には 183 日。
Schengen 90/180 については、専用の Schengen 計算ツールをご利用ください。IRS の Substantial Presence Test には、 SPT 計算ツールをご利用ください。
The threshold is not always 183
Reaching for a 183-day calculator and then applying 183 to a jurisdiction that uses a different number is a common and expensive mistake. Set the threshold field to your own rule:
- 180 days: Thailand, on the calendar year.
- 182 days: India, on a financial year running 1 April to 31 March, and Malaysia on the calendar year. India also has a second route at 60 days for people with substantial presence over the preceding four years.
- 184 days: New York, and in practice any rule written as "more than 183 days", which includes the statutory-residency tests in New Jersey, Massachusetts, Connecticut and Pennsylvania, each of which also requires a permanent place of abode.
- 200 days: Oregon and Hawaii.
- 270 days: Idaho, alongside a home kept in the state for the whole year.
- About 214 days: Alabama and Oklahoma, whose statutes are written as seven months rather than as a number of days, so the day figure is an approximation and the shorter reading is the safe one.
- No fixed threshold: California, where more than nine months creates a rebuttable presumption of residence while less than nine months creates no presumption the other way, and Illinois, which turns on domicile and purpose rather than on a day count.
- Fewer than 90 days: Cyprus can treat you as resident on 60 days when its other conditions are met in the same year, and the UAE has a 90-day route for specified people with a permanent place of residence and a job or business there.
「1 日」の数え方
ほとんどの管轄地域では、暦日にわずかでも滞在があれば 1 日としてカウントします。深夜 0 時時点の滞在を求める地域もあります（UK SRT）。通過日を除外する地域もあります。詳しいガイドを読む： 183 日ルールの解説。
The conventions that decide whether a given date lands in your total:
- Any part of a day: New York and several other US states count any presence at all, including a connection between two flights, as a full day. It is the most punitive convention and the one to assume when you do not know which applies.
- Presence at the end of the day: the UK statutory residence test generally counts a day only if you are in the UK at midnight, with limited exceptions for transit and for exceptional circumstances beyond your control, plus a separate deeming rule for people with several UK ties.
- Both ends of the trip: the Schengen 90/180 rule counts the day you enter and the day you leave in full. That is an immigration limit rather than a tax test, and it runs on a rolling 180-day window instead of a year.
- Days that are excluded: the US substantial presence test disregards, among others, days of exempt individuals, days you are in transit between two points outside the United States and are in the country for less than 24 hours, and days you could not leave because of a medical condition that arose while you were there.
- A window that moves: some rules count within any rolling twelve-month period rather than a fixed year, so the window shifts by one day every day and there is no 1 January reset to plan around.
Common mistakes and edge cases
Almost every day-count dispute comes down to one of these:
- Counting nights instead of days. A Friday to Sunday trip is three days under most rules, not two. Repeat that across twenty trips and your count is twenty days light.
- Assuming the year starts on 1 January. The UK tax year runs 6 April to 5 April, Australia's income year 1 July to 30 June, and India's financial year 1 April to 31 March. Set the window before you enter a single trip, or every total is measured over the wrong period.
- Treating the threshold as a safe harbour. Staying under the number is not the same as being non-resident. Domicile, a home kept available to you, where your family lives and where your economic interests sit can each make you resident on far fewer days, and several systems have a deliberate low-day route.
- Forgetting that residence usually covers the whole year. Crossing on 26 December generally makes you resident from 1 January, not from 26 December. Split-year and part-year reliefs exist, UK split-year treatment and the US dual-status year among them, but they are specific reliefs with their own conditions rather than the default outcome.
- Mixing the immigration clock with the tax clock. A 90/180 visitor limit and a 183-day tax test are different rules with different windows and different consequences. Being comfortably inside the 90 days says nothing about your tax position, and a stay that is perfectly legal on immigration can still create a residence question.
- Counting from memory at the end of the year. Tax authorities expect contemporaneous evidence: boarding passes, hotel folios, card transactions. Where the burden of proof sits with you, an undocumented day tends to be counted against you, and reconstructing a year afterwards is usually the moment people discover they were already over.
- Watching only one country. Days out of one place are days in another. Cutting to 150 days somewhere while spending 200 days somewhere else swaps one residence question for a worse one.
If more than one jurisdiction is in play, count them together in the multi-country day counter.
Setting the calculator to your rule
The calculator counts every distinct calendar day inside the window you set, counting entry and exit dates in full and de-duplicating days shared by overlapping trips. To match your rule:
- If your rule says "183 days or more", enter 183. The threshold is reported as met on the day the count reaches it, which is what that wording means.
- If your rule says "more than 183 days", enter 184, the first day that actually makes you resident. The same logic turns any "more than N" rule into a threshold of N plus one.
- Set the window to the jurisdiction's own year, not the calendar year, unless the two are the same.
- Add one row per continuous stay, entry date and exit date. Days covered by two overlapping rows are counted once.
- Enter trips you have not taken yet. The projected crossing date is calculated from everything in the list, so scheduled travel shows you the date you would cross before you commit to it.
Where a rule excludes certain days, transit days under the US substantial presence test for example, leave those days out of the trips you enter rather than expecting the calculator to know about them. It counts calendar days, it does not apply any one jurisdiction's exclusions.
183 日ルールでできること、できないこと
183 日ルールはどの国でも同じですか？
いいえ。暦年で 183 日というのが最も一般的なパターンですが、しきい値も対象期間もさまざまです。184 日を用いる米国の州もあれば、任意のローリング 12 か月間で 183 日を数える国もあり、日数に加えて住居や本籍（domicile）の要件を組み合わせる国もあります。だからこそ、この計算ツールではしきい値と期間の両方を設定できます。
到着日と出発日は合計にカウントされますか？
管轄地域によります。1 日の一部でも滞在があれば 1 日とみなす地域が多い一方、深夜 0 時の滞在を数える地域や、通過について例外を設ける地域もあります。迷ったら保守的に（両方の日を含めて）数え、日ごとの記録を残しておきましょう。
183 日未満なら税務上の居住地を避けられますか？
必ずしもそうではありません。日数はトリガーの 1 つにすぎません。本籍、恒久的住居、家族や経済的な結びつき、条約のタイブレーカーによって、はるかに少ない日数で居住者となることがあります。しきい値を下回ることは有利ですが、保証にはなりません。
どの課税年度の期間を使うべきですか？
ほとんどの国は暦年で測定します。英国は 4 月 6 日から 4 月 5 日、オーストラリアは 7 月 1 日から 6 月 30 日で、ローリング 12 か月を用いる地域もいくつかあります。旅程を追加する前に、ご自身の管轄地域に合わせて期間を設定してください。課税年度計算ツールで主要な管轄地域の日付を確認できます。
しきい値を超えるとどうなりますか？
一般に、その管轄地域はその年についてあなたを税務上の居住者として扱うことができ、多くの場合、全世界所得への課税と新たな申告義務が生じます。例外、条約による救済、年途中の取り扱いは地域によって異なるため、依拠する前に専門家に確認してください。
この計算ツールは旅程を保存しますか？
いいえ。すべてブラウザ内で動作します。予測とアラートを伴う継続的な追跡が必要なら、Tax Days の iPhone アプリが旅程を端末内に安全に保存します。
Sources & further reading
Every rule on this page is drawn from primary sources. Verify the current law before making a residency decision.
- [1]OECD Model Tax Convention, Article 4 (Resident) tie-breaker （新しいタブで開きます）OECD
- [2]26 U.S.C. § 7701(b), definition of resident alien and the substantial presence test （新しいタブで開きます）Office of the Law Revision Counsel
- [3]Substantial Presence Test （新しいタブで開きます）IRS
- [4]Finance Act 2013, Schedule 45, the statutory residence test （新しいタブで開きます）legislation.gov.uk
- [5]Income Tax Act, section 250(1), person deemed resident (sojourning 183 days or more) （新しいタブで開きます）Justice Laws Website, Canada
- [6]NY Tax Law § 605 (resident definition) （新しいタブで開きます）NY Senate
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