I had an assault charge 14 yrs ago and it was dismissed, but now my employer wants proof, do I need to provide this?

First how did they find out about it in the first place, since almost no applications ask for arrests, only convictions.

But if they did a check and it is not showing dismissed, they can ask for it, you would go to the courthouse and try and get a copy of the records.

NCIC ( in the US) only show convictions, some private agency searches may show up a lot of things that were dismissed, or explunged.

So first who told them this ever happened, and if you told them, why