Add spaces: Fortheowneritcouldbecostly,atworst,threatensanadditionalpaymentofCroatianimportsalestaxintheamountof25Percentofthevalue,adoubledutypaymentaswellasaheftypenalty.
For the owner it could be costly, at worst, threatens an additional payment of Croatian import sales tax in the amount of 25 Percent of the value, a double duty payment as well as a hefty penalty.