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How to Write a Formal Sunset Announcement

Writing & Email · 4 min read · 2026-08-16 · Updated 2026-08-26

Team guiding an old machine into storage while its replacement continues operating

Writing a formal sunset announcement starts with two language choices: grammatical voice and the preposition used for the timeline.

Many formal notices use the passive voice: "X will be sunset on [date]." They also need a time word such as "by," "on," "in," or "over." Clear wording helps readers identify what is ending and understand the schedule.

Quick check: Deadline, date, or span?

Use the article’s rule to judge this specific draft.

Why passive voice dominates formal announcements

Passive voice is common in formal notices. It keeps the focus on the product or service that will end.

"The v1 API will be sunset on March 1, 2027."

"This legacy benefit will be fully sunset by the end of Q4."

The progressive active form works well when the announcement emphasizes a transition that is already underway.

"We are sunsetting the on-premise version over the next six months."

Neither voice is always "correct." Passive voice emphasizes the product or service. Active voice emphasizes the team making the change, while the progressive form presents the transition as ongoing. Choose the emphasis that fits the announcement.

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Matching the preposition to the kind of date

Match the time word to the schedule. "By" gives the last date for completion. "On" names one date. "In" names a period, such as a month or quarter. "Over" describes a change that takes place across a span of time.

The wrong word can change the stated schedule. Beyond that first sentence, a formal notice should explain who is affected, what support remains, and what action readers need to take.

The one preposition that's always wrong

Do not use "sunset until [date]" as the direct pattern for stating an end date. The phrase "sunset until Q3" is unnatural; use "by Q3," "in Q3," or "over the course of Q3" based on whether you mean a deadline, a period, or a span. However, We will not sunset the service until Q3 is correct because until follows the negative verb and marks how long the service will continue.

Before you send the notice, check each part. Make sure the voice fits the event. Then make sure the time word states the schedule you mean.

Why both pieces matter more in a formal document

A quick team message may have enough context to explain a vague phrase. A formal announcement often reaches a larger audience. It may appear in a client email, a leader's deck, or an official policy update. Readers need the date, expected impact, and next steps in plain words.

Check voice and time separately instead of relying on one "does this sound right" test. Good grammar cannot tell readers whether a date is firm or a decision is final. Confirm the "approved schedule" and "decision owner" with the team responsible for the change, then state any open points clearly.

Practice scenarios

Practice using sunset in situations like:

  • choosing between passive and progressive active voice for a sunset announcement
  • matching the right timeframe preposition to a deadline, a date, or a span
  • catching an incorrect "sunset until" before an announcement goes out

Useful practice phrases:

  • "The v1 API will be sunset on March 1, 2027."
  • "This legacy benefit will be fully sunset by the end of Q4."
  • "We are sunsetting the on-premise version over the next six months."

Draft the next sentence

A clear sunset sentence needs the right voice and timeline preposition.

The complete announcement should then explain the impact, final service date, available support, required migration steps, and where readers can ask questions.

Lyra Practice helps advanced non-native English professionals learn the nuance of high-value workplace expressions and practice using them in realistic scenarios, so their English sounds natural, precise, and senior at work. Try Lyra Practice.

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