How do I update my tax ID number with WooCommerce Payments?

You can update the tax ID number associated with your account at Stripe.com. You can reach your account at Stripe.com via WooCommerce Payments:

Go to Payments > Settings.
Click Manage in Stripe to be taken to Stripe.com
Click the pencil icon in the Business Details (company accounts) or Personal Details (individual accounts) section.
Find the relevant Tax ID field (EIN, SSN, etc.) and click the Replace button
Enter the new number.
Click Done.

Editing the tax ID number from the Stripe.com dashboard via WooCommerce Payments.

Once you complete these steps, you will be prompted to agree to an ownership transfer agreement. You can do this by clicking the Add button, then following the prompt to accept the terms and conditions.