Which email address should I use when setting up my business account?

Use an email address you can access and are authorised to use for the business. You can verify your email or use Google sign-in during signup. Choose the address that should receive account-related correspondence, rather than an address controlled only by someone who is temporarily helping with setup.

For a company, make sure the person applying is allowed to act for that company. Using a business email does not replace the owner or entity checks. If you entered the wrong address, ask support how to correct the application rather than starting several versions under different addresses.