TDS Remitted in Excess

Well yes...

I feel that he can re file his TDS return and get the 1800 Rs. exess back from the Department..

In my opinion what is the harm if he has deposited excess TDS and has issued Form 16A for the same amount.The contractor can claim the same in his Income Tax Return.

As far deduction of lesser TDS is concrened your client can have a talk with the contractor and can adjust the excess amount against the outstanding balance of the contractor.

If the contractor is a one time contractor then Jiten's suggestion can be applied. But for that your client has to re-issue Form 16A to the contractor.