Ivy uses Stripe for processing online payments. Here is how Stripe explains this $1 charge:

"When storing customer details or using Checkout to collect payment data, we send over a request to the issuing bank for a $1 authorization to verify that the card is issued and the bank will allow it to be authorized. Regardless of whether or not the authorization is declined, we reverse our authorization request immediately. However, even if the bank declines the authorization, some people may still see an authorization for $1 on their credit card statement. The important thing to remember is that this is not a charge, and it will disappear from their statement; depending on the bank, it will be removed from their statement in anywhere from a few minutes to a few weeks.

Stripe will first attempt a $0 authorization in all cases except AMEX (which doesn’t support $0 authorizations - we try a $1 auth right away with AMEX.) If the $0 authorization fails, we’ll then attempt a $1 authorization."