Plain English definitions

IR35 and contractor tax glossary

38 definitions of the terms UK limited-company contractors, umbrella workers and freelancers actually need to understand. Written by specialist contractor accountants. All figures verified for 2026/27.

IR35 and contractor tax glossary

IR35 fundamentals

IR35

Chapter 8 (intermediaries legislation)

Chapter 10 (off-payroll working)

Personal service company (PSC)

Inside IR35

Outside IR35

Status tests

CEST

Status Determination Statement (SDS)

Mutuality of obligation

Control

Substitution

Reasonable care

Client-led disagreement process

Blanket determination

Off-payroll mechanics

Deemed employment payment

Fee-payer

End client

Small company exemption

Off-payroll set-off (offset)

Limited company tax

Dividend

Corporation tax marginal relief

Director's loan / s.455

Business Asset Disposal Relief (BADR)

Members Voluntary Liquidation (MVL)

TAAR (winding-up / phoenix)

Umbrella and employment

Umbrella company

Assignment rate

Apprenticeship Levy

Key Information Document (KID)

Umbrella JSL (April 2026)

Managed Service Company (MSC)

Employment Allowance

Expenses, VAT and compliance

24-month rule

AMAP mileage

Flat Rate Scheme

Limited cost trader

VAT registration threshold

Day rate