Basic salary, HRA, and conveyance are definitely included in the calculation of gross salary. Special allowance, other allowances, and incentives are questionable in terms of accountability for calculating gross wages.
As per ESI law, any amount paid after a gap of two or more months will not be considered for inclusion in the wage ceiling of INR 15,000/- or INR 21,000/- (from December 2016). However, this issue arises for the initial months of the contribution periods, i.e., April or October. Deductions will be made for the rest of the months if the gross wages exceed the wage limit by the end of the contribution period.