Yes. Laying a bet involves betting against an outcome. For instance, if you are betting on a soccer match between Liverpool and Everton, a lay bet on Everton would be betting against an Everton victory. A draw or a Liverpool win would see you win the bet, but an Everton win would leave you liable for the winning bettor's profit. So whilst it is possible to win whilst laying, you do need to have enough funds to cover any losses.