Good point! Under Social Security Contributions and Benefits Act 1992... might not mean the same kind of "benefit"
lawvolumes.dwp.gov.uk/docs/a2-2501.pdf
Part I CONTRIBUTIONS (S4) (1)-(6) Payments treated as remuneration and earnings. Page 2.2521/2.2522
Refers to ITEPA 2003. I'm fairly sure that a persons tax code is not reduced by any spell on welfare benefits because of the £30,000 limit.
Not sure whether NI is deductable?