Your bonus is almost certainly entirely descretionary in contractual terms, so your employer is under no obligation to pay it. I wouldn't hand in my notice until I had the filthy lucre in my account. Tell your new employer of the circumstance - explain that you just can't afford to walk away from the bonus. You may find they offer you a 'golden handshake' bonus to replace it! [Some years ago, it was possible to do 'golden handshake' bonuses tax-free, I don't know if this is still the case].