Via ALPS, which bills itself “the nation’s largest direct underwriter of lawyers’ malpractice insurance”: “Closure letters – What Are They and Why Should Lawyers Bother with Them?” —

• “In the Claims world, we love closure letters. Unfortunately, we rarely see them in the files – perhaps that is because attorneys who send closure letters may not be sued as much as those who do not send closure letters! When we use the term, “closure letter” we are referring to a letter that the attorney sends the client at the conclusion of the matter on which the attorney has assisted the client. The closure letter can take many forms.”
• “Many attorneys have misconceptions about closure letters. Attorneys want clients to consider the attorney as “their attorney” so that the next time the client has legal work, the client will automatically call that attorney. We have worked with attorneys who deliberately did not send a closure letter because they wanted the client to think of the attorney for future work and were afraid the closure letter will send a message that the attorney is completely through with the client and never wants to see the client again. Instead, the client forgot what the attorney told him or her and later sued claiming the client believed the attorney was going to do something wholly outside the scope of the original representation. With no closure letters, the claim can turn into a he-said-she-said litigated matter.”
• “If the attorney re-frames the closure letter in terms of a thank-you letter, far from offending the client, it can convey the message that the attorney has appreciated the client and looks forward to working with the client again on future matters… Another advantage is that the date of the closure letter is a bright-line date from which the statute of limitations may start running.”
• “For attorneys who work with business clients, a closure letter can be an excellent tool to clearly state who is responsible for business filings, corporate records, etc. A closure letter is a service to your client in clarifying the work and what, if anything, the client needs to think about in the future. Client’s memories fade and the letter is a useful tool in keeping the record straight. So, for 2020, we would suggest a New Year’s resolution to send closure letters in all client files!”

They offer some additional guidance on the substance of closing letters in: “Don’t Kiss Off The Importance Of Closure Letters.”

And for even more detail on navigating the topic of concluding client matters, the Advocate offers: “Terminating the attorney-client relationship.”