By way of a reminder, under the legislation, where an umbrella company doesn't correctly operate tax, HM Revenue & Customs (HMRC) can recover the resulting liabilities – including unpaid Pay As you Earn (PAYE) and employee and employer National Insurance contributions (NICs) - from the recruitment agency with the contract to supply the worker to the end client.
Where there's no agency in the chain, the liability can instead sit with the end client.