A trade union which is not under the control of an employer or group of employers or of one or more employers' associations, and is free from interference by an employer or any such group or association (arising out of the provision of financial or material support or by any other means) (section 5, Trade Union and Labour Relations (Consolidation) Act 1992 (TULRCA)) .

Section 6 of TULRCA gives the certification officer power to certify that certain trade unions are independent. A certificate of independence is conclusive evidence that a trade union is independent. A refusal, withdrawal or cancellation of a certificate is conclusive evidence that the trade union is not independent.

For further information, see Practice note, Trade union recognition (2): the recognition process.