Taxability of Unbilled revenue in case of Construction contracts

[MUKUNDHONKAN]

In respect of certain Construction Company, billing is done on completion of milestones as per client's requirement  even if work is completed.

Company  has decided  at  the year end such completed work be booked as Un build revenue .

Pl. let us know taxability implications uner Income tax , VAT & Service tax.

It will be nice if I get relevant  case laws   regards Mukund M Honkan