BAKTHAVATSALAM, J.

These batch of cases raise identical and similar issues pertaining to the constitutional validity, legality and propriety of levy of sales tax and other allied taxes on transactions familiarly known as "works contracts". Though the nature of such works contracts are varied and multifarious, their grievance and concern are common, except certain differences peculiar to the type of contracts which ultimately have relevance only in respect of the individual assessment and determination of the liability of the assessee concerned, but so far as the constitutional and legal issues raised are concerned, there are no differences, as such. In these batch of writ petitions, some of the assessees have challenged the validity of the amendments introduced by the Tamil Nadu General Sales Tax (Fourth Amendment) Act, 1984 (Tamil Nadu Act 28 of 1984) and rules 6-A and 6-B introduced with effect from October 1, 1984 or the Tamil Nadu General Sales Tax (Fourth Amendment) Act, 1986 (Tamil Nadu Act 42 of 1986) introducing section 3-B and the Fourth Schedule to the main Act with effect from June 26, 1986 and amendments to rule 6-B, etc., at different stages obtaining interi