Hello there, @SvetaZ.

Allow me to join the thread and help fix and share a little more information about the R03 code you've received.

You'll receive the R03 code when the account number used does not correspond to the individual identified in the entry or a valid account. To fix the problem, you may need to check your bank account information in the Merchant Services Center, and fix any mistakes, or update your bank information for payments/deposits.

For further details on how to update your bank information where payments are deposited to, you may check this article: Change bank account information where payments are deposited.

You may also check this article for more information about resolving ACH returns: Resolve ACH returns on your payments account.

On the other hand, you may get in touch with our Merchant Support Team to check why the invoice shows as paid when you didn't apply a payment to it. For the support's contact information, you may check this article: Which Payments product do you need help with?.

Stay posted if you have any other QuickBooks or payment concerns, I'll be always here to help you. Wishing you the best!