I have a client who is currently claiming SSP but wants to give up his job and claim IB and IS instead (he is currently claiming DLA mid rate care). Would there be any problems? I have tried to understand sch 12 SSCBA but being Monday morning it's not making a lot of sense. 

Thanks

Its rarely in anybody's interest to give up their job when sick, regardless of whether they are on SSP or not. Apart from burning bridges, my understanding is that if they wait for the employer to finish them, they will be paid full notice. I strongly recommend that you refer them to an employment rights adviser to check on the full implications of what they decide.

There's nothing stopping him claiming IS while he is on SSP, unless he has other income which takes him over aplicable amount. If thats the case then, (teaching granny to suck eggs alert) a better off calculation is obviously needed.