How to deliver bad news to a client
Lead with the news. Everything you put in front of it reads as a stall.
The situation
The number is worse, the date has moved, or the thing they were counting on will not happen. Your draft opens with two paragraphs of background because that feels kinder.
It is not. A client reading around for the actual news is doing work you should have done, and the delay reads as evasion the moment they find it.
Why it is hard
Burying bad news is a politeness strategy that misfires in writing. In conversation, preamble gives the listener time to adjust; in email the reader scans for the point, finds it in paragraph three, and retrospectively reads everything before it as management. Leading with the news and following with the plan reverses that: the reader knows where they stand by line two and reads the rest as help rather than as cushioning.
What to actually write
Two versions of the same message. Same facts, different posture — which one is right depends on the relationship, not on which is “better”.
Common questions
Should I call instead?
For anything that changes money or a committed date, send the email first so they have it in writing, then offer the call. Do not use a call to avoid putting it on record.
How much detail about the cause?
Enough to show the delay is being spent on their behalf. Beyond that it becomes self-justification.