The filing calendar comes from outside and does not move. A checklist per client, with what was requested, what arrived and what is still missing, turns a deadline into a list rather than a weekend.
The revenue hides in the hours nobody writes down: the call between meetings, the quick answer, the correction that took twenty minutes. Captured against the client, they are either billed or given away on purpose.
Work done, work billed and work paid are three different lists. Held as one, the gap shows while there is still time to chase it rather than a year later.