TL;DR

Chapter 8 refers to the off-payroll working rules in the UK that apply to medium and large private sector companies engaging contractors through personal service companies (PSCs), in force from April 2021. It extended the public sector framework (Chapter 10) to the private sector, shifting the responsibility for IR35 status determination from the contractor to the engaging business. Small businesses are exempt.

The Structure of Chapter 8

Chapter 8 did not create a new test for employment status — it changed who must apply the existing IR35 test. Before April 2021, private sector contractors were responsible for self-assessing whether their engagements fell inside IR35. That self-assessment model had been in place since 2000 and was widely seen as producing under-compliance, since contractors had a direct financial incentive to assess themselves as outside IR35.

Chapter 8 transferred that determination responsibility to the client company. A medium or large business engaging a PSC contractor must assess whether the engagement resembles employment, communicate that determination in a Status Determination Statement, and ensure PAYE is operated on the contractor's fees if the determination is inside IR35.

The size threshold that determines whether a business falls under Chapter 8 mirrors the Companies Act definition of a small company. A business is small if it meets two of three criteria: fewer than 50 employees, annual turnover below £10.2 million, or balance sheet total below £5.1 million. Businesses below this threshold remain outside Chapter 8, meaning their PSC contractors continue to self-assess. Subsidiaries of large groups may fall under the parent group's size for this purpose even if the subsidiary itself is small.

The rules apply to the engager, not the worker. A contractor supplying services to a small client is outside Chapter 8 regardless of how large or sophisticated their PSC is. The same contractor supplying the same services to a large corporate the following month falls inside it.

IR35 and the Employment Status Test

The underlying test under Chapter 8 is whether the worker would be an [employee](/glossary/employee) if the PSC did not exist. HMRC's Check Employment Status for Tax (CEST) tool is the most commonly used assessment mechanism, though it is not the only one and has been criticised for limitations on edge cases.

The three primary factors the test considers are control, substitution, and mutuality of obligation. Control asks whether the client dictates how, when, and where the work is done. A contractor who shows up at a client's office five days a week, uses the client's equipment, and is managed by the client's team looks much more like an employee than a supplier. Substitution asks whether the worker can send someone else to do the work. A genuine, exercised right to substitute another qualified person supports an outside determination. Mutuality of obligation asks whether there is ongoing commitment on both sides — if the client must offer and the worker must accept further work, that looks like employment.

Secondary factors include financial risk (does the contractor invest in their own business and risk a loss?), integration (is the worker embedded in the client's organisation?), and provision of equipment.

Implications for Recruiters and Staffing Agencies

Staffing agencies sit in the supply chain and bear liability if they get Chapter 8 compliance wrong. The fee-payer — typically the agency that pays the contractor's PSC — must operate PAYE when an inside determination has been issued, even if the agency disagrees with the client's assessment. The tax liability for failing to do so falls on the fee-payer.

Agencies need processes for collecting SDSs from clients, verifying the determination before the engagement starts, and maintaining records that demonstrate PAYE was operated correctly on inside engagements. Clients who refuse or fail to provide an SDS create a problem: in that situation, the legislation defaults to treating the engagement as inside IR35.

The blanket inside determinations that many large organisations issued when Chapter 8 came into force created significant disruption in the UK contractor market. Contractors who had legitimately operated outside IR35 found themselves inside IR35 without individual assessment, which HMRC had warned against but did not initially act to prevent.

In Practice

A medium-sized professional services firm begins engaging a marketing contractor through the contractor's PSC in March 2021. The firm issues an SDS in April, determines the engagement is inside IR35, and notifies both the contractor and the agency in the supply chain. The agency, as fee-payer, begins deducting income tax and National Insurance from the contractor's invoices and remitting to HMRC. The contractor disagrees with the determination and raises a formal challenge. The firm reviews within 45 days, maintains its inside determination, and documents the reasoning. The agency continues to operate PAYE while the disagreement is outstanding.

Key Facts