[NEMDF]

I saw in a business letter a couple days ago something along the line of “.... long term care insurance would be a compliment to your existing employee benefits....”.

I think they should have used complement. ??

[SAJ]

They should indeed have used 'complement', in the sense of an enhancement of the existing benefits.

You might consider offering the addressee of this letter a compliment for having sensibly chosen the long-term care that complements the existing benefits...assuming, of course, that it **is** a sensible choice, which in some cases it may not be.