I once had a negative balance for a few months. I have been cheated by a buyer for about $450. I refused to pay it right away and eBay gave my information up to collections agency. Sooner or later they reached out to me and threatened that I pay as soon as possible or I will face some serious consequences. I would recommend you pay what you owe them as fast as possible, if you at all care about your eBay account or your personal information on it. Good luck!