you don't report it as a dividend. it is nontaxable return of capital that reduces your basis in that C-Corp stock.
Since you say you disposed of the stock you show the reduced cost on form 8949. Unless this was privately issued stock, you would get a 1099B from the brokerage holding it and they should automatically reduce your cost basis but you will have to check to make sure. If the sale was in 2020, there's nothing to report in 2019.
