If you’re stuck, call your former employer’s payroll department. They likely have your TIN on file. They get a weird power trip from holding this information. Be polite. Ask nicely. They’ll probably email it to you within an hour.
Or, try the IRS2Go app if you’re in the U.S. It’s a little blue and white app. You can check your refund and retrieve your TIN. It’s like a wallet for your taxes. Handy and mildly adorable.
HOW TO VERIFY TIN NUMBER ONLINE? UPDATED PROCESS TO VALIDATE YOUR TIN