If you are a builder you should have deposited the choice of rate by 20 may and if you don't give any letter to Department you would autonaautomatbe considered under lower rate and in that case you need to reverse the credit in the same month in which you were not eligible for credit if you don't do that you'll have to pay interest also.
If you have received advance you have to pay GST on same you can't wait till occupancy certificate.
Yes you can show 30% presumptive taxation.
It depends on why you had selected ITR 3 in previous year and now why are you selecting ITR 4.
If he cancelled his registration in September then before cancelling and filling final return he should have filed annual return.
Sir you have asked too many questions and we are professional and not 24 hour help line number and taxfull is just a website it does not have any employees who give you service we professional people give you service so if you are in a hurry it would be better if you hire a professional to answer all your query or have a phone consultation.
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