Income calculation

As per bills generated..

but sir in future if i do not get that payment then...........

Do not issue final invoice. If you get payment then issue final invoice. further if you issue invoice say in march then you have to pay gst in april, but if you receive payment in july then you will have problem so better issue invoice in july when you receive payment

Claim loss/credit  as amount not recoverable, even after due compliances...

Sir the case is I have raised bills of consultancy to few companies...now most probably I will receive payment in next financial year..so is it possible that I calculate them in my next year income when I will receive payment....my purpose is not saving any tax ..but I want to pay tax only on the payment I have received

Well, you may, but there will be mismatch of income and TDS deducted by your clients over the bills/services received by them.

TDS mismatch will not be an issue since you can carry forward your uncliamed TDS credit to the next AY and then claim it in that year in which you will declare that income.