Paid down is an English phrasal verb that denotes the act of reducing the amount of debt owed or decreasing the balance owed. Its antonyms, therefore, refer to the opposite of this action. Some of the antonyms of paid down include borrowing, increasing, adding to, expanding, growing, and mounting up. When we borrow, we are effectively increasing our debt rather than reducing it. Similarly, when we add to or expand our accounts payable, we are not paying down any debt. Instead, we are increasing our balance. In short, all actions that result in an increase in debt or balance owed are antonyms of paid down.