Although consumers often have multiple payment methods at their fingertips, such as cash and credit/debit cards, prior research is silent on how consumers choose between them. We home in on a key element of purchase — purchase justifiability — that affects how consumers choose to pay. Analysis of 118,042 real-world purchases and six experiments reveals that when consumers are motivated to forget (vs. remember) a purchase because they see it as difficult (vs. easy) to justify, they have an increased preference to pay with cash (vs. card) because cards create a “paper/electronic trail” that aids memory retrieval. These payment preferences are strongest among consumers most likely to recall/track their card spending, and manifest only when card expenses are trackable. We reconcile our results with the classic effect of payment method on pain of paying and discuss implications for merchants and for financial institutions designing payment methods of the future.