Formal alternative to "that'll do" [closed]

Solution 1:

A more formal way of expressing such could be: ... that will suffice.

The idiom that will do has in its definition a more formal synonym: TFD

That is enough, that will suffice.

to suffice: OED

To be enough, sufficient, or adequate for a purpose or the end in view.

As in:

New York Times Aug 22, 2019 Just a bowl of it with a dab of yogurt would suffice [will do], but for the full effect it should be topped with a savory stew of chicken or lamb.

Suffice comes from a combination of the Latin words sub ("under") and facere ("make") that together mean "meet the need of." This need is usually the bare minimum — sufficient!

Solution 2:

The problem with "That'll do." and "Will that do?" is not that they are informal, but that they may be considered condescending, rude, or impatient.

As a statement of acknowledgement, a simple thanks should suffice.

• Thank you for [completing my request for _____].

As a question, it may be dropped entirely from your sample statement.

• Attached are the screenshots you requested. [Explanation for technical stuff.]

If you wish to add an interpersonal touch, you may use something like the following:

• I hope this resolves _____. Please let me know if there is anything else I can do for you.

Also, do not end the letter with "Thanks". Not only is the word informal, the other party has not done anything for which you should thank them. The traditional closing is "Sincerely".