But it has to be done, money has to come in so that it can go out, and let the account cycle continue. That's why it's so important to send monthly statements.
There are numerous reasons debtors don't pay. A lack of money is obviously going to be an issue, but not having seen the initial invoice can easily be remedied by sending a reminder statement around the 10th of the month. Especially if it's a client/customer who receives many invoices each month... it's always possible one slipped through unseen.
When it comes to accounts payable, always reconcile the supplier statement or report against the invoices in your system. Email for a copy of any missing invoices, get them in the system and, hey presto, we're set to pay our creditors the correct amount on the 20th of the month.
It's a simple double checking practice that can save a lot of time.
It's also an excellent prompt for some creditors who don't work on a 20th of the month payment schedule, they just pay once the statement is reconciled. If only they were all like that... and all toilets were self-cleaning.