Word Choice – Assistance In Versus Assistance With

Christina’s question: “Which sentence is correct — Thank you for your assistance in this matter or Thank you for your assistance on this matter?”

BizWritingTip response: Unfortunately, neither sentence is correct. “Assistance on” is incorrect. The prepositions following assistance are “in,” “with,” or “to.”Although many writers interchange them, “assistance with” is used to indicate helping someone with someone or something. “Assistance in” indicates helping to do something.
Here’s another way to determine the correct word: If there is only a noun following, use “assistance with.” If there is a verb following, use “assistance in.”

Examples (with before a noun)
Can you provide assistance with the room set-up?
Thank you for your assistance with this matter.

Examples (in before a verb)
She will be giving us some assistance in preparing the report.
We are looking for someone to provide assistance in planning the event.