Chapter 10 of Part 2 of the Income Tax (Earnings and Pensions) Act 2003 contains the off-payroll working rules. These applied to public sector clients from 6 April 2017 and were extended to medium and large private-sector clients from 6 April 2021. Chapter 10 is the part of IR35 under which the end client decides status, not the contractor.
Under Chapter 10 the end client must issue a Status Determination Statement (SDS) for each engagement, and the fee-payer (usually the agency closest to the PSC) operates PAYE and employee National Insurance, and pays employer National Insurance at 15% on top, before paying the net amount to the PSC. There is no 5% expenses allowance under Chapter 10, unlike Chapter 8.
Chapter 10 applies only where the end client is medium or large. If the client is small under the small company exemption, responsibility falls back to the PSC under Chapter 8. The statutory hooks are ITEPA 2003 ss.61K to 61X, with the deemed direct payment in s.61N. For the practical mechanics of how inside-IR35 income is taxed under each regime, see deemed employment payment.