So you performed receivables confirmation procedure at period end and a receivable balance for say customer A was not confirmed. A fact it was not confirmed and you didn’t receive a reply for your request in itself should indicate that there’s a possible impairment indication. More so, as the days pass, it’s also not paid.
When normally there are customers who pay a few days later, if they didn’t reply to your request, it’s another matter. You should be more worried for such customers and carry out additional routines usually done in such situations.
The routines to follow through include sending a reminder, a new invoice with additional charges applied in case of late payments, calling the customer and asking for third party to start collecting for the receivables. I would even say that it is the normal order of things. Obviously, depending on your previous experience with the customer it may vary, but the rule still applies. Whenever you feel there will be problems, act before things go bad.