There will be a $1 charge that will appear on your account to test the validity of the banking information entered which is known as a verification fee. A verification fee will take place any time the billing information is updated or changed.
Typically, the verification fee is a pending authorization, which is voided. You should not see the $1 transaction go through as an actual charge. It will show as pending and then be removed from the account usually after a few business days.
Occasionally, this charge may be slightly higher than $1 due to exchange rates and taxes, however, the charge will never be more than $2. If you have any concerns about the validity of a charge on your account from iThemes, you can reach out to our Sales Support here.