In order to update your tax ID number, login to your business account, and go to the 'Admin' section. Then, at the bottom of the first link, titled Business Contact Info, you'll see a section for your business Tax ID number. Don't have one? Here's a link to the US Govt Tax ID number information page:

Get your Small Business Tax ID Number

Update your profile with your new Tax ID number, click 'Save' at the bottom and you're done!

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