Every delay email I wrote for the first four years of freelancing had the same shape.
Paragraph one, context. Paragraph two, what went wrong, in detail, because I wanted it understood that the situation was genuinely unusual. Paragraph three, a bit more context I had forgotten. And then somewhere near the bottom, buried, the only sentence the client actually needed: the new date.
I thought I was being transparent. What I was doing was making the client read four hundred words to find out whether their Monday was ruined.
The client is scanning for one thing
Put yourself on their side. They open the email, see the words "unfortunately" and "delay" in the first line, and immediately need to know one fact so they can work out what it breaks. Do they need to tell someone? Move a meeting? Change a launch date?
Until they have the new date, they cannot think about anything else. So every sentence of explanation you place above it is a sentence they read while mildly panicking, and panic makes explanation read as excuse.
The reason has not changed. The order has changed what the reason means.
The order that works
New date first. Reason second, briefly. What you are doing about it third.
"The homepage build will be ready Thursday 24 July instead of Tuesday 22nd. The API documentation from your side had a gap I had to work around, which cost about two days. Everything else is on schedule and I have shifted the review call to Friday to match."
Fifty words. The client knows in the first sentence what they are dealing with. The reason is there, stated once, without defensiveness. And the third part matters more than people realise, because it tells them they do not need to manage the consequences themselves.
Compare that to the version where the date is in the last line. Same facts. Completely different reception.
Do not explain twice
The strongest instinct when delivering bad news is to keep going. You explain, then you sense it landed badly, so you explain again in different words, then you apologise, then you explain the apology.
Length signals guilt. A short message about a delay reads as a professional handling a scheduling change. A long one reads as someone who knows they have done something wrong, and the client picks that up and adjusts their view of the situation accordingly.
State the reason once. Resist the second pass. This is much harder than it sounds and I still fail at it when I am nervous.
Say it early, which is the actual hard part
Most delay emails go out too late, because the day you realise you might slip is not the day you are certain, and it feels premature to raise it.
But a client who hears on Tuesday that Friday is at risk has options. A client who hears on Friday morning has none, and the absence of options is what turns a schedule problem into a trust problem. In my experience clients forgive slipped dates fairly easily. They do not forgive finding out late.
If you are not certain yet, say that. "There is a chance this moves to Thursday, I will know by tomorrow morning." That is not weakness. It is the thing a client actually wants from someone managing part of their project.
Two words to cut
Unfortunately. It adds nothing except a warning that bad news is coming, which delays the news by one word while raising the tension. The delay is unfortunate whether or not you label it.
Hopefully. As in "hopefully by Thursday." Hope is not a commitment and clients hear the hedge clearly. If Thursday is uncertain, say what it depends on. If it is not, drop the word.
When it was actually their fault
This comes up constantly and it is the reason most delay emails go wrong. The feedback came four days late, or the assets never arrived, and now the date is moving because of them.
Two failure modes here. Either you swallow it entirely, which teaches them the deadline was soft and guarantees a repeat. Or you make the email about blame, which is satisfying for an hour and expensive for a year.
The way through is to state the dependency as a neutral fact in the same breath as the date, and then move on immediately. "Ready Thursday 24 July. The copy arrived on the 17th rather than the 15th, so the build shifted by the same two days. No action needed from you now."
That last sentence is the important one. It closes the topic. You have made the record without asking them to respond to an accusation, which means nobody has to defend anything and the relationship survives intact.
The general rule I have landed on: say the true thing, once, in the flattest words available, and then keep the project moving in the very next line. Almost all the difficulty in these messages comes from trying to say the true thing without saying it.