Am I able to use the email used for my Express account to open a Standard account with Stripe?

If you already have an Express account, you are not currently able to sign up for a Standard (Stripe.com) account with the same email. Instead, you can use an email alias (e.g., bob+stripe@example.com instead of bob@example.com) if you would like to sign up for a Standard account.

However, this rule does not apply in reverse: if you already have a Standard account, you can sign up for an Express account using the same email.

Some helpful tips: