TRADE UNION AND LABOUR RELATIONS (CONSOLIDATION) ACT 1992 ss.213 and 251A
Until 30th August 1993 ACAS was forbidden to charge for advice (TULRCA 1992, s.213(1)). That was changed with effect from 30th August 1993 (TURERA 1993, s.43, which amends TULRCA 1992, s.213, and TURERA 1993, s.44, which inserted a new s.251A into TULRCA 1992).
Under TULRCA 1992 s.251A, ACAS may now "charge a fee for exercising a function in relation to any person" and must do so if the Secretary of State so directs.
See also notes at ACAS generally,