In Short: IRS Form 6166
Form 6166 is a letter on US Treasury letterhead certifying that a person or company is a US resident for tax purposes. Foreign tax authorities and payers ask for it before they apply a reduced tax treaty rate or a VAT exemption.
- How to get it: file Form 8802, Application for United States Residency Certification. Form 6166 is the letter the IRS sends back.
- Fee from October 1, 2026: $105 per application for individuals and $230 for companies and other non-individuals, paid on Pay.gov.
- Timing: apply at least 45 days before you need the letter. The IRS contacts you after 30 days if processing is delayed.
- Who qualifies: US citizens, green card holders, US corporations and US-owned LLCs that filed their US return as US residents.
- Who does not: a single-member LLC owned by a non-US person. A disregarded LLC is not a US resident on its own, so certification follows the owner.
When a US business earns money abroad, the foreign country can withhold tax at its full domestic rate unless the business proves it is a US tax resident. The proof that country accepts is IRS Form 6166. With it, the payer applies the lower rate in its tax treaty with the United States, or the tax office grants a VAT exemption.
This guide covers what Form 6166 is, who can get one, how to apply on Form 8802 and the mistakes that delay it. All figures come from the IRS Instructions for Form 8802 (Rev. October 2026).
Form 6166 at a Glance
| What it is | A letter of US residency certification on Treasury letterhead |
|---|---|
| What it is for | Claiming tax treaty benefits or a VAT exemption in another country |
| How to request it | Form 8802, Application for United States Residency Certification |
| Fee | $105 per application for individuals, $230 for non-individuals (from October 1, 2026) |
| Payment | Pay.gov, searching for “IRS Certs” |
| Submit by | Mail or fax; individuals can also use the IRS mobile-friendly online form |
| Processing | Apply at least 45 days before you need the letter |
| Period covered | One calendar year per certification; current and prior years can be requested |
What Is IRS Form 6166?
Form 6166 is not a form you fill in. It is the certificate the IRS issues after it approves your Form 8802 application. It states that the named person or entity is a resident of the United States for purposes of US taxation, for the calendar year shown.
Foreign payers, banks and tax offices use it to confirm that you qualify for the treaty between their country and the United States. It cannot be used to prove that US tax was paid, for example to support a foreign tax credit claim in another country.
When Do You Need Form 6166?
- A foreign client withholds tax on your payment. Many countries withhold tax on service fees, royalties, interest or dividends paid to a foreign company. Presenting Form 6166 lets the payer apply the reduced treaty rate.
- You are claiming a refund of tax already withheld abroad at the full rate.
- You are claiming a VAT exemption in a country that requires proof of US residency.
- A foreign bank or platform asks for proof of US tax residency as part of its own treaty paperwork.
The reverse case is a foreign-owned company receiving US income. A non-US company does not use Form 6166; it gives the US payer a Form W-8BEN-E to claim treaty rates. For background on how treaties work, see our guide to tax treaties and double taxation.
Who Can Get Form 6166?
The IRS certifies residency when the applicant is subject to US tax because of residence, citizenship or place of incorporation, and has filed the required US return for the period. The table shows how that applies to common business owners.
| Applicant | Eligible? | What the IRS looks for |
|---|---|---|
| US citizen or green card holder living in the US | Yes | A filed Form 1040 |
| US citizen or green card holder living abroad | Yes, with a statement | A filed Form 1040; a penalties of perjury statement and documentation if you filed Form 2555 or are a dual resident |
| US corporation (C corporation) | Yes | A filed Form 1120; residency comes from incorporation in the US |
| Single-member LLC owned by a US person | Yes, through the owner | The owner’s filed US return; Form 6166 certifies that the single owner is a US resident |
| Multi-member LLC taxed as a partnership | The US partners only | Form 6166 lists the partners who are US residents; each partner’s authorization, such as Form 8821, is attached |
| Single-member LLC owned by a non-US person | No | A disregarded entity is not a US resident, and its owner is not one |
| Anyone who filed as a nonresident | No | Form 1040-NR or Form 1120-F filers are not certified |
A US corporation owned by a non-US person can be certified, because residency follows the place of incorporation. Whether the other country then grants the treaty rate depends on that treaty’s own rules, including limitation on benefits clauses that look at who owns the company. Check those rules before you rely on a reduced rate.
Why a Foreign-Owned LLC Cannot Get Form 6166
This is the most common misunderstanding among non-resident founders. A single-member LLC is a disregarded entity for US income tax: it files Form 5472 with a pro forma Form 1120 as an information return, but its income belongs to its owner. The IRS instructions state that a disregarded entity is not a US resident and that treaty benefits are available only if its single owner is a US resident.
A founder living outside the United States who owns a US LLC is a resident of their home country, not of the United States. The LLC therefore cannot obtain Form 6166, and the founder claims treaty benefits, if any, as a resident of their own country.
How to Apply for Form 6166 on Form 8802: Step by Step
- Confirm you filed the return. The IRS issues Form 6166 only if you filed the required US return for the period, or the return is not yet due and you filed the most recent one that was due.
- Download Form 8802 and fill in the applicant’s name, TIN or EIN and address.
- Line 7: the certification year. Enter the 4-digit calendar year you need certified. You can list the current year and prior years on one application.
- Line 8: the tax period of the latest return that was due, in YYYYMM format. For example, a Form 1040 filer applying on August 1, 2026 for a 2026 certificate enters 202512.
- List every country you need a certificate for. The fee is per application, not per country or year, so one Form 8802 covering several countries costs one fee.
- Add the required statements. Individuals sign a penalties of perjury statement that they are and will remain US residents for the year. Single-member LLCs enter the owner’s details on line 6.
- Pay the fee on Pay.gov under “IRS Certs”: $105 for individuals or $230 for non-individuals, by bank account or card. Upload a copy of the Form 8802 with the payment and write the confirmation number on page 1.
- Sign and submit by mail, by fax or through the IRS Mobile-Friendly Forms version, which is open to individual applicants only. Married couples filing jointly both sign.
Where to Send Form 8802
| By mail | Department of the Treasury, Internal Revenue Service, Philadelphia, PA 19255-0625 |
|---|---|
| By private delivery service | Internal Revenue Service, 2970 Market Street, BLN# 3-E08.123, Philadelphia, PA 19104-5016 |
| By fax | 877-824-9110 (US only) or 304-707-9792 (from inside or outside the US); up to 10 applications and 100 pages, with a cover sheet stating the page count |
| Online | IRS mobile-friendly Form 8802, for individual applicants only |
| Questions | 267-941-1000 |
How Long Does Form 6166 Take?
The IRS asks applicants to submit Form 8802 with full payment at least 45 days before they need Form 6166, and it contacts you after 30 days if processing is delayed. Applications for the current year are accepted from December 1 of the prior year: a 2027 application postmarked before December 1, 2026 is returned.
Common Mistakes That Delay Form 6166
- Applying before the return is filed. No filed return, no certificate.
- Filing one application per country. Each Form 8802 costs a fee; list every country and year on one form.
- Forgetting the Pay.gov upload. The fee payment must include a copy of the Form 8802.
- Applying for a disregarded LLC with a foreign owner. The IRS cannot certify it.
- Leaving out the Form 2555 statement as a US citizen living abroad.
- Applying too late. Foreign payers withhold at the full rate until they receive the certificate.
Get Your US Company Set Up Correctly
BusinessAnywhere forms US LLCs and corporations for $0 plus the state fee, gets the EIN for $97 and files Form 5472 with the pro forma Form 1120 for foreign-owned LLCs for $497 a year through its US LLC tax filing service. For treaty planning across two countries, book a tax and residency consultation.
Frequently Asked Questions
What is IRS Form 6166?
Form 6166 is a letter on US Treasury letterhead certifying that a person or entity is a US resident for tax purposes. Foreign countries accept it as proof for tax treaty benefits and VAT exemptions.
How do I get Form 6166?
File Form 8802, Application for United States Residency Certification, with the user fee paid on Pay.gov. The IRS reviews the application and sends Form 6166.
How much does Form 6166 cost?
From October 1, 2026, the user fee is $105 per Form 8802 for individuals and $230 for non-individuals, regardless of how many countries or years one application covers.
How long does it take to get Form 6166?
Submit Form 8802 with payment at least 45 days before you need the letter. The IRS contacts you after 30 days if processing is delayed.
Can a foreign-owned LLC get Form 6166?
No. A single-member LLC is a disregarded entity, and the IRS certifies it only if its single owner is a US resident. A non-US owner is not, so the LLC cannot be certified.
Can a US citizen living abroad get Form 6166?
Yes. US citizens remain subject to US tax. If you filed Form 2555 or are a dual resident, attach a statement and documentation to Form 8802.
Is Form 6166 the same as Form 8802?
No. Form 8802 is the application you file. Form 6166 is the certificate the IRS issues in response.
Can I file Form 8802 online?
Individuals can. The IRS offers a mobile-friendly digital Form 8802 for individual applicants. Companies and other entities file by mail or fax.
This guide summarizes the IRS Instructions for Form 8802 (Rev. October 2026). It is general information, not tax advice. Treaty benefits depend on the treaty with each country, so confirm your position with a tax professional.
