To get a foreign tax identification number, you file an application with the relevant country’s tax authority, prove your identity with a passport or national ID, and wait several weeks for the number to issue. The exact form, the accepted documents, and whether you need a local representative vary by country, but the core is the same everywhere: legal name, proof of identity, a stated reason for the request, and sometimes a resident who can receive mail for you. Before you start any application, check whether an identifier you already hold will do the job.
Check Whether You Already Have One
Most countries issue a tax number to every resident or citizen, and foreign institutions will accept it. In the United States, your Social Security Number is your TIN for federal and international tax purposes.1Internal Revenue Service. Taxpayer Identification Numbers (TIN) In the United Kingdom, your National Insurance Number plays that role.2GOV.UK. National Insurance: Introduction: Your National Insurance Number Ireland uses the Personal Public Service Number for tax and government services.3Revenue. Personal Public Service Number (PPSN)
Some countries don’t issue a separate tax number to every citizen. In those cases, a passport number or national identity card number often works as a substitute when a foreign bank or brokerage asks for a TIN. The OECD maintains a portal where each participating country publishes its rules on TIN issuance, format, and acceptable alternatives.4OECD. Tax Identification Numbers That portal is the best first stop. Check it before starting an application you may not need.
The General Application Pattern
Every country has its own form, but the shape of the process is remarkably consistent. You submit an application to the national tax authority with proof of identity, proof of address or a stated reason for needing the number, and, in some cases, the details of a local representative. Documents almost always have to be originals or copies certified by the issuing agency. Photocopies rarely work, and notarized photocopies typically don’t either.
Where a country requires a power of attorney for a representative or a consular submission, the document often has to be apostilled. An apostille is a standardized certificate recognized by countries that participate in the 1961 Hague Convention, confirming that a document is genuine.5Department of State. Preparing Your Document for an Apostille Certificate In the United States, apostilles for federal documents come from the State Department, and apostilles for state-level documents come from the relevant secretary of state’s office.
Applying for a U.S. ITIN as a Foreign National
If the foreign number you need is a U.S. one, the form is Form W-7, the Application for IRS Individual Taxpayer Identification Number.6Internal Revenue Service. About Form W-7, Application for IRS Individual Taxpayer Identification Number The IRS issues ITINs to people who have a U.S. tax filing obligation but aren’t eligible for a Social Security Number. Applying directly with the IRS is free.
On the W-7 you pick a reason code. The instructions list several: nonresident aliens claiming a tax treaty benefit, nonresident aliens filing a U.S. tax return, and U.S. resident aliens who meet the substantial presence test but can’t get an SSN, among others.7Internal Revenue Service. Instructions for Form W-7 You also enter your country of citizenship and a mailing address. The reason code matters because each category triggers different documentation requirements.
Acceptable Identification Documents
A valid passport is the simplest option because it’s the only document that proves both identity and foreign status on its own. Without a passport, you need at least two documents from the IRS’s accepted list, and at least one must include a photograph. The list includes:
- Foreign driver’s license, which proves both identity and foreign status
- National identification card showing your name, photo, address, date of birth, and expiration date
- Civil birth certificate, required for applicants under 18 who don’t submit a passport; this proves foreign status only if issued by a foreign government
- USCIS photo identification or a U.S. visa
- Foreign military identification card
- Foreign voter’s registration card
All documents must be originals or certified copies from the issuing agency. Notarized photocopies won’t be accepted. This is where many applications stall, because people understandably don’t want to mail their original passport to Austin, Texas.
How to Submit
You have three routes, and the choice mostly comes down to whether you’re willing to part with your originals for several weeks.8Internal Revenue Service. How to Apply for an ITIN
- By mail. Send the completed W-7, your tax return (if required), and original or certified documents to the IRS ITIN Operation in Austin. Originals come back after processing but are out of your hands for weeks.
- In person at an IRS Taxpayer Assistance Center or VITA site. Free, and staff can authenticate documents and hand them back the same day.
- Through a Certifying Acceptance Agent. A CAA reviews the W-7, authenticates most supporting documents on the spot, and mails the package for you. This is fee-based, but you keep your passport.
A CAA is particularly useful if you live outside the United States and can’t visit an IRS office. CAAs can authenticate most documents except foreign military IDs and certain dependent documents, which must still be mailed as originals.
How Long It Takes
The IRS estimates about seven weeks under normal conditions. During tax season (January 15 through April 30) and for applications sent from overseas, expect nine to eleven weeks.9Internal Revenue Service. Individual Taxpayer Identification Number (ITIN) Applications filed right before April hit peak volume and the longest waits at the same time. If a specific filing deadline is driving you, start months ahead.
ITIN Expiration and Renewal
An ITIN doesn’t last forever. If you don’t use it on a U.S. federal tax return for three consecutive tax years, it expires on December 31 after that third year of non-use.10Internal Revenue Service. How to Renew an ITIN This catches people who had a brief window of U.S. income and then didn’t file for a few years. When the ITIN is needed again, the old number can’t just be used. You submit a renewal on Form W-7, provide the same identification, and wait for processing.
If an expired ITIN appears on a return that hasn’t been renewed, the IRS will process the return but may delay any refund and disallow certain credits until the renewal clears. Renewal is free when you apply directly, same as the initial application.
Getting a TIN in Other Countries
For a number issued outside the U.S., the OECD’s TIN portal lists the format, issuing authority, and requirements for each participating country.4OECD. Tax Identification Numbers Start there rather than with third-party guides, which go stale quickly.
Two examples show how the practical path can vary. In Italy, non-residents can apply for a codice fiscale through Italian consular authorities in their home country, without traveling to Italy.11Agenzia delle Entrate. Tax Identification Number for Foreign Citizens In Spain, non-residents apply for a Número de Identidad de Extranjero either in person at a police station in Spain or through a Spanish consulate abroad, and they can appoint a representative with a power of attorney if they can’t appear personally.12Ministerio de Asuntos Exteriores. Foreigner Identity Number (NIE) Consular routes exist in many countries and are worth checking before you book a flight.
When You Need a Local Fiscal Representative
Some countries require non-residents to appoint a fiscal representative before issuing a tax number or before you can conduct certain transactions. The representative is a local resident, often an accountant or attorney, who receives official correspondence from the tax authority on your behalf and helps you meet local filing obligations. The requirement is most common in European countries for non-EU residents.
Portugal is a familiar example. Non-EU residents historically needed a fiscal representative to obtain a NIF. Portugal has loosened this for Portuguese citizens living outside the EU who sign up for electronic notifications through the finance portal, but the requirement still applies to most non-EU foreign nationals.13Governo de Portugal. Non-Residents Exempt from Appointing a Fiscal Representative in Portugal If you’re buying property or starting a business in a country that requires representation, budget for the cost. Representatives typically charge an annual fee, and failing to appoint one when required can stall the application or trigger administrative penalties.
Setting up the relationship usually requires a formal power of attorney. Depending on the country, the document may need to be notarized and apostilled before it will be accepted.
Common Mistakes That Delay Applications
The most frequent problem is a name mismatch. The name on your application has to match your passport or primary ID exactly. If your passport reads “María Elena García López” but you write “Maria Garcia” on the form, expect a rejection or a slow back-and-forth. Accented characters, middle names, and compound surnames all matter.
The second most common issue is unacceptable copies. Photocopies almost never work. Most tax authorities want originals or copies certified by the issuing government agency. For U.S. ITIN applications specifically, notarized photocopies are not acceptable, only originals or copies certified by the issuing agency. A Certifying Acceptance Agent eliminates this problem for most documents.
The third is underestimating timelines. If you need a foreign TIN to open a bank account or close a real estate transaction by a specific date, start the application months ahead. Published processing times are estimates under normal conditions, and delays from incomplete applications or peak-season backlogs can easily double the wait. Filing during the quieter months and checking every field before you submit are the two things most within your control.