I was in almost the same situation as you a while ago, though the sign-on bonus was slightly less than yours it was still a large chunk to just pay back. In th

I was in almost the same situation as you a while ago, though the sign-on bonus was slightly less than yours it was still a large chunk to just pay back. In the end, I couldn't stand being at the job another 8+ months and so left and negotiated a repayment agreement with them. They weren't so happy about that and wanted to add interest, fees and so on but after I explained that they could accept the monthly repayments OR basically get nothing and go through a long drawn-out legal process to try and reclaim some of it they reconsidered. The sign-on bonus is a tiny fraction of their profits but if you owe it then it is only fair to pay it back, especially if agreed to in a written contract. For my situation, I appealed to the fact that I spent a portion of the sign-on bonus in order to relocate and get my life setup for this new job and so it wasn't such an easy thing to pay back in one go. You're not going to win any friends by leaving so soon anyway so my advice would be to arrange a payment plan, explain that the job just isn't what you're looking for and leave as soon as you find another position you like. If the new position has a sign-on bonus too even better but be careful of the same thing happening again.