Check your tax return, tax notices, or official tax registration documents
Look on your tax identification card or certificate if your country issues one
Visit your country’s tax authority website and use the TIN lookup or verification service
Contact your local tax office or revenue department directly
Ask your employer, accountant, or tax preparer if they have it on file
Review business registration documents if the TIN is for a company
Check bank, customs, or import-export records if the TIN was previously used there
Use your passport, national ID, or business registration number to request the TIN from the tax authority