Firms that close the month calmly tend to follow the same rhythm every time. The exact days depend on your local deadlines, but the structure is universal.
Day 1: open the period for every client
Open the new collection period for all active clients at once, so everyone receives the same checklist on the same day. Clients who prepare early can start immediately.
A few days before the due date: remind only what is missing
A reminder that lists the two missing items is far more effective than a generic “please send your documents”. Clients who are already complete should not be reminded at all.
Continuously: review as documents arrive
Reviewing in small batches keeps feedback fast. Accept what is complete; reject what is not with a short, specific reason so the client can fix it the same day.
Due date: look at the overdue list, not the whole list
On the due date, focus only on overdue clients and what exactly each of them is missing. That is usually a short list - and a phone call is often faster than another e-mail.
After closing: adjust the checklist
If the same item is rejected again and again, the instruction is probably unclear. Improve the wording before the next period.