Methods, apparatus, and systems for funding transactions disclosed herein may operate to: receive, for a transaction, a request to debit a first amount from a primary funding source; determine that a second amount of funds available from the primary funding source is less than the first amount requested for the transaction; compare a maximum backup funding amount with a total amount debited from a backup funding source to fund previous transactions associated with the primary funding source, with the maximum backup funding amount being previously set as an amount available from the backup funding source; and to provide an indication that at least part of a difference between the first amount and the second amount can be drawn from the backup funding source based on determining that the total amount has not reached the maximum backup funding amount.