In this paper we analyse whether the recording behaviour of consumers keeping a payment diary changes over the diary period. Using data from a large study on the payment behaviour of German consumers we find that individuals tend to report a higher number of transactions on the first day of the diary period than on subsequent days. Contrary to existing literature we also find that the number of small cash payments recorded does not decrease during the one-week diary period. Our findings indicate that short diaries may be enough to reflect adequately the payment behaviour of all consumers. However, the precision of the estimates increases with longer diaries, at small additional costs. Longer diaries are especially helpful when it comes to analysing subgroups of payment types or rare events.