Name the impact without exaggerating it
Describe who had to wait, worry, redo work, spend money, or make a choice with incomplete information. For a message about how to follow up on a requested scope change, use this factual base: summarize the deliverable, version, requested input, owner, and effect on the schedule.
Make repair practical
Offer the repair you can actually complete, with ownership, timing, and any limit stated honestly. Give a small set of options and explain which default plan applies if the real deadline passes. Make the immediate next step clear enough that the recipient can answer without reconstructing the entire history.
Let future behavior carry the proof
Do not bury a scope or price change, threaten the relationship, or pretend silence means approval. Use the contract and documented escalation route for legal, payment, privacy, or security decisions. A promise inside a message is weaker than a visible change in what you do after it.