To backdate a linked ESA claim (when in the support group), do you need a sicknote for the backdated period? 

Hi

I have a client who was claiming ESA and was in the support group.  He then withdrew his ESA claim to start work.  However, the job only lasted a week.  Then, due to mental illness he has claimed nothing for the past two months.  I am aware that he can make a linked claim for ESA and get the money backdated for two months.  However, would he need a sick note backdated for two months? 

The hospital where he is staying will only issue him a sick note for the past two weeks (his date of arrival at the hospital). 

Thanks