End a working relationship with a client politely

Write a message ending our working relationship with {{client}}, for me to send. It should make clear that the decision is final, be professional enough that neither side's reputation suffers, and be practical about the remaining work, files and payments.

Background, for your understanding only (not to repeat in the message): {{background}}

What we agreed in writing about ending the work (notice period, final invoice, ownership of files), quoted:
"""
{{agreement_terms}}
"""

Today's date: {{today}}
End date, and what I will finish before then: {{end_plan}}
Money owed in either direction: {{money}}
What I will hand over, and how (files, logins, notes): {{handover}}
Someone I could refer them to, if I want to offer one: {{referral}}

Write:
1. The message, 120 to 220 words, in this order: the decision and the end date in the first two sentences, one neutral sentence on why (for example "Our ways of working are no longer a good fit, and I don't think I can give you the service you need."), what I will finish, the handover, the final invoice or refund, the referral if I have given one, and a courteous close.
2. A short checklist for me: notice dates, items to hand over, access to remove, and the final invoice, using only the facts above.

Rules:
- Do not list complaints, assign blame, or repeat anything from the background, even if it is true. A neutral reason is enough, and it gives the client nothing to argue with.
- Do not promise refunds, extra work or deadlines I have not stated.
- Follow the notice terms in our agreement. If my end date does not meet the notice period, use the earliest date that does, counted from today, and flag the difference to me above the draft.
- If my handover plan and the agreement differ, for example the agreement ties ownership of files to payment, ask me rather than choosing.

If our agreement is silent on something the message has to cover, such as who owns unfinished files, leave it out of the message and list it as a question for me, with a suggestion to check with a lawyer if the contract is large or disputed.