Off-Payroll Working Rules Explained
How the 2021 reforms shifted IR35 status responsibility to engagers — and what it means for contractors and umbrella workers.
Last updated: April 2026
What Changed in 2021
Before April 2021, a contractor operating through a limited company was responsible for assessing whether their own engagement fell inside or outside IR35. If HMRC disagreed, the contractor faced the tax liability.
The off-payroll working rules (sometimes called Chapter 10 rules or "IR35 reform") reversed this: the end client (medium and large private sector, and all public sector) must now assess the IR35 status of each contractor engagement and communicate the decision in a Status Determination Statement (SDS).
Key Point for Umbrella Workers
The off-payroll rules only apply to contractors using intermediaries (limited companies). If you already work through an umbrella company, you are employed under PAYE and the rules do not apply to you — you are already being taxed correctly.
Who the Rules Apply To
| Engager Type | Responsible Party | Since |
|---|---|---|
| Public sector (any size) | End client (engager) | April 2017 |
| Medium/large private sector | End client (engager) | April 2021 |
| Small private sector | Contractor's limited company | Still self-assessed |
| Umbrella company workers | N/A — already employed (PAYE) | Always |
Timeline of IR35 Reform
IR35 introduced (Intermediaries Legislation) — contractor self-assesses
Off-payroll rules introduced for public sector — engager responsible for status
Private sector extension delayed 12 months due to COVID-19
Off-payroll rules extended to medium/large private sector engagers
Mini-budget repeal reversed — rules remain in force
Rules unchanged — engagers still responsible for medium/large sector
Disagreeing with a Status Determination
If you receive an SDS stating your engagement is inside IR35 and you disagree, you can formally challenge it. The engager must consider your representations within 45 days and either maintain or revise the determination. If they fail to respond in time, the liability transfers back to the engager.
Tools like HMRC's CEST (Check Employment Status for Tax) tool can help assess status, though HMRC only stands behind CEST results when the tool is used accurately and in full.
Learn more about status determinations →
HMRC: Understanding off-payroll working