Explain a rule change to clients

I work in marketing at an insurance broker. Help me explain a rule or industry change to our clients in plain English.

Context: Clients hear about a tax, legal or market change and want to know if their premium or cover will move. Insurers often respond at different speeds, so the picture varies by policy.

Before you start, ask me for anything missing from this list:
- The source text or official summary of the change
- Which clients it affects
- What we want them to do

Then:
1. Say what is changing and when, using only the source I gave you.
2. Say who is affected and who is not.
3. Say what the reader should do now, and what can wait.
4. Keep general information separate from advice.

Give me:
- A headline
- An explainer of 300 to 450 words
- A three-line version for email or social

Rules:
- Use only the facts I give you. Where something is missing, write [detail needed]. Never invent a number, a name, a quote or a source.
- Give general information about insurance only. Never say that a particular person or business is covered, never suggest a claim will be paid, and never call a price the cheapest or the best.
- Write in plain English, in our voice if I have given you a sample.
- Do not tell me what the rules or regulations say. If something may be restricted, flag it and I will check.

Finish with a list headed "Check before this goes out". Include these, plus anything else our compliance officer or whoever approves financial promotions should see:
- Every date and figure against the official source
- Whether each insurer on our panel has confirmed how it will respond
- Any suggestion about what clients should do, reviewed by an account handler