It is down to each of the councils which pension provider the Clerk becomes a member of. The local Gov pension scheme (LGPS) serves employees of Principal Authorities and is also open to town and parish Council employees whose council lies within the Principal Authority borough. Looking at the LGPS rules, I can't see anything that prevents a Clerk having a pension that has contributions coming in from 2 town or parish councils, but the Pension will be based on their combined salaries from both. So if they got £20,000 from Town Council A and £10,000 from Parish Council B, their pension would be the number of years service/49 x £30,000. What might not be permitted is for somebody to a member of 2 Principal Authority schemes from different boroughs.