A claimant calls in to the local social security office and voluntarily hands over their payment book, either because they are about to start full time work or to move in with a partner in FT work. When does IS entitlement end? Is it the day they hand the book in, the date of CoC or sometime else? In this situation, is the Department required to issue a supersession decision that IS has ceased from such and such a date?

I would imagine that in this circumstance, a written statement would be taken in some form, outlining the CoC. IS entitlement would then cease on the day of the CoC. This could of course be before or after the book was handed in. The practicalities are that benefit weeks rarely coincide with real life events, so I would expect that a few days overlap one way or the other will occur.

to the best of my knowledge, the DWP treats it as a voluntary withdrawal of the claim, and does not give any formal decision.

jj

From past experience, DWP usually investigate why the claim has ended, in case it was fraudulent in the first place, so the client would be asked to provide proof of the new job starting and then the benefit would be adjusted accordingly.