Quick answer
If you searched for the IRS 6166 form or 6166 tax form, the key distinction is that Form 8802 is used to request U.S. residency certification, while Form 6166 is the certification letter the IRS may issue. Tax Paperwork does not issue, request, submit, upload, pay for, mail, fax, or monitor Form 6166.
Source and advice boundary
Use the linked IRS Form 8802, Form 8802 instructions, and Form 6166 pages as official source starting points. This guide is education-only and does not provide tax, legal, treaty, residency, certification, payment-channel, filing-channel, or status advice.
Form 8802 is the application or request
The IRS Form 8802 page says to use Form 8802 to request Form 6166, a letter of U.S. residency certification for income-tax treaty or VAT-exemption purposes.
Tax Paperwork can organize known Form 8802 facts in a browser-local draft preview, but it does not submit the request, handle Pay.gov, upload files, pay fees, mail, fax, or monitor processing.
Form 6166 is the IRS-issued certification
The IRS Form 6166 page describes Form 6166 as a U.S. residency certification letter and says the IRS procedure for requesting it is submitting Form 8802.
That means a local Form 8802 draft is not Form 6166 and is not proof that the IRS will issue a certification or that a foreign requester will accept one.
Where Tax Paperwork fits
Use the preview only to collect known individual applicant, certification year, country, and purpose facts against the current IRS Form 8802 source.
Stop before relying on a draft when treaty eligibility, residency position, entity status, unfiled-return statements, foreign withholding, certificate timing, or foreign acceptance is uncertain.
Official sources to check
- IRS About Form 8802 for the official application source.
- IRS Instructions for Form 8802 for current request mechanics and documentation requirements.
- IRS Form 6166 page for the certification description and source notes.
How this page was prepared
This page starts from the official sources linked below, keeps filing-channel decisions with IRS.gov or qualified professionals, and shows the same limits that appear in the public draft workflows.
Tax Paperwork pages are maintained under the editorial policy and checked against the public-preview evidence described on the preview confidence page. Last page review: June 14, 2026.
Current Tax Paperwork boundary
Tax Paperwork is not tax, legal, accounting, entity-structuring, treaty, fiduciary, valuation, or filing-channel advice. It is not IRS.gov and does not submit, transmit, fax, mail, upload, pay, or monitor IRS paperwork.