Natural Migration

I may have imagined this but I seem to recall a regulation that says that if a person on legacy benefits moves in with a partner who is already getting UC then the only option is a joint UC claim.

My cl has had a Mandatory Migration letter but when contacted about help to make the UC claim we discovered that they were living with someone who gets UC. Should it be a change of circs on the partners claim rather than managed mig?

Yes, Reg 7 of the UC (Transitional Provisions) Regs says they are assessed as a couple from the beginning of the AP in which they got together, and that any IS or HB terminates from the same date.  Tax Credits would always have terminated, but no new claim can be made as a couple by virtue of Reg 6A; and ESA(ir) or JSA(ib) is abolished from the start of the AP by Article 4(2)(c) of the No 9 Commencement Order.

And for the avoidance of doubt, Reg 50(2)(b) of the UC(TP) Regs prevents them from having transitional protection.