If you aren't going to start work for them until after your op, then you won't qualify to receive SSP from them. Your current employer should issue you with an SSP1 form (stating that they're no longer paying you SSP cos you've left). If you take this to the DWP, they'll hopefully sort you out with Incapacity Benefit. If you are actually starting work for your new employer before the op, then you can be considered for SSP as soon as you've done some work for them, as long as your earnings are above the national insurance lower earnings limit. You can only receive SSP for a maximum of 26 weeks in one go though, and all periods of sickness that are less than 56 days apart, even if they were with a different employer or were for a different reason count as being 'in one go', so it sounds as though you may be nearing the end of your allowance. If you do exhaust your allowance, your employer at the time will have to issue you with the SSP1 to take to the DWP/JobCentrePlus for Incapacity Benefit, this time stating that you've had your maximum.