A tax residency certificate is an official letter in which a tax authority confirms that a person or company is resident there for tax purposes, so a treaty partner can grant relief. In the United States it is Form 6166, requested on Form 8802, and since 1 October 2026 the IRS charges $105 per individual application and $230 for entities.
What is a tax residency certificate
A tax residency certificate is proof, issued by your home tax authority, that you are resident there under its tax law. The other country needs it before it applies the reduced rate or exemption in a double tax treaty.
The certificate grants no relief by itself. HMRC's guidance, updated 26 August 2026, states that the overseas authority decides whether relief is granted, and points to a refund claim where tax was already paid.
How to get Form 6166 from the IRS
A US resident files Form 8802, Application for United States Residency Certification, and the IRS replies with Form 6166, a computer-generated letter on Department of the Treasury letterhead.
The applicant pays the user fee on Pay.gov (the search term is "IRS Certs"), uploads a copy of the completed Form 8802 at payment, which the IRS has required since 29 September 2024, and enters the e-payment confirmation number on page 1. The IRS will not process a Form 8802 without that number.
The form then goes by mail, private delivery service or fax. A current-year request also needs a statement signed under penalties of perjury that the applicant is a US resident.
What does Form 8802 cost from 1 October 2026
Form 8802 costs $105 for an individual applicant and $230 for a non-individual applicant, such as a company or trust, per form.
For an individual, the $105 applies regardless of the number of countries or tax years on the form, and the IRS encourages applicants to combine every request on one Form 8802.
Illustration: a US citizen resident in New York needs certificates for France, Japan and Germany for 2025 and 2026. Listing all three countries and both years on one Form 8802 costs $105. Three separate forms cost 3 × $105, or $315. The same combined request from a US company costs $230.
When should you apply for Form 6166
The IRS asks for the application, fee paid, at least 45 days before Form 6166 must reach the foreign payer or authority, and contacts the applicant after 30 days if processing is delayed.
A current-year request has a start date. The IRS returns any request for a current-year Form 6166 postmarked before 1 December of the prior year, so the earliest postmark for a 2027 certificate is 1 December 2026.
Illustration: a foreign withholding agent needs a 2027 certificate by 15 March 2027. Counting back 45 days gives a mailing date of 29 January 2027. The same form can also cover any number of prior years.
Who cannot get a US certificate of residency
The IRS refuses Form 6166 to anyone who did not file a required US return or filed as a nonresident on Form 1040-NR. The same applies to anyone who used a treaty tie-breaker to be treated as resident of the other country.
US citizens and green card holders who file Form 2555 must attach a statement and documents explaining why they qualify. The instructions warn that under many US treaties, citizens and green card holders without a substantial presence, permanent home or habitual abode in the United States during the year are not entitled to treaty benefits. The substantial presence test field note and the United States tax guide cover the rest.
Heed's reading: for Americans abroad, the filing history decides the answer. A Form 2555 filer living outside the United States may hold a US passport and still fail to qualify for Form 6166 under the treaty in question.
How the UK and Singapore issue certificates
HMRC issues a certificate of residence to a UK resident claiming under a double taxation agreement, and a letter of confirmation where no treaty applies or proof of residence is needed for another purpose.
Applications go through HMRC's online service or by post to HMRC BX9 1AS for individuals. HMRC needs the treaty, the country, the income type and the period, and it certifies no future date. An individual who has not yet filed a Self Assessment return gives the number of UK days and, below 183 days, the reasons for UK residence under the statutory residence test.
IRAS issues a COR to Singapore tax residents claiming treaty benefits. Applicants use a QR code or online application for their profile, foreign employees without Singpass email a spreadsheet form, and an overseas form needing IRAS endorsement goes by post. IRAS states processing takes 2 to 3 weeks. Rates are in the Singapore tax guide.
- United States · Form 8802, answered with Form 6166 · $105 individual, $230 entity from 1 October 2026 · apply 45 days ahead
- United Kingdom · HMRC online service or post · no fee listed in HMRC's guidance · no future dates certified
- Singapore · IRAS online application by profile, or form · no fee listed on the IRAS page · 2 to 3 weeks
Day counts drive every one of these answers, which is why the tax residency use case starts there. Heed monitors international tax law changes across every jurisdiction we track and sends personalised alerts before they affect your situation.