The key account at D+32
Your biggest customer is a month late. Your accountant is scared to call them. Your cash flow can't wait.
Tier-aware tone is the whole trick: a Gold account gets a note that reads like a colleague checking in, not a collections script. The relationship stays warm; the invoice still moves. And if it reaches D+60, the desk stops and hands you the full history with three suggested paths — the hard call stays human.