Resolve an unapplied payment
The following applies only for customers with invoiced billing accounts.
If you pay for your Google Apps subscription using an invoiced billing account and send us a payment without noting the invoice the payment applies to, you may have an unapplied payment. If this happens, you’ll see a message next to your billing account's Amount due in your Google Admin console.
Email payment instructions to Google Apps support
To apply the payment to your account balance, email Google Apps Support with instructions on how to apply the payment and to which invoices. For example, you can apply the entire payment to one invoice or split it among several invoices. If you do the latter, just be sure to include the invoice numbers and the amounts we should apply to each one.
Learn more about viewing your invoices.