The Offline payment gateway can be used for mail in cash or check payments. As for online check payments, which are just bank transfers, are supported by our Stripe payment gateway via ACH Debit Transfer payment method. Note Stripes usage of ACH Debit Transfer requires a Plaid account as they use them for the direct debits. BECS Direct Debit (AU bank accounts) and SEPA Direct Debit (EU bank accounts) are also supported.