1) if flat is not registered in your name then tripartite agreement with builder and buyer is necessary 

2) If you are selling the property before the issuance of the completion certificate, it is a supply of under-construction property and GST would be payable 

3) Since you bought property only in march 2022 sale as on date would attract short term capital gains tax 

4) if the booking right in an under-construction house is not held at least 36 months before the sale, the resultant gains shall be taxable as a short-term capital gain.

on one hand you say that the sale agreement was registered and on the other hand you say that the flat is not yet registered in your name

GST is to be paid on every installment until OC is received

your query does not disclose whether you have made full payment or part

considering your holding period is less than 3 years, you will incur short term capital gains tax

- GST is applicable on under-construction properties that have not yet received the OC , however However, if the seller has received the completion certificate before the agreement, you don't have to pay GST.

- Further, the GST not applicable in case of resale or ready-to-move flats, hence no GST applicable as it is already paid once.

- It will be considered as short terms capital gains.

Firstly you are yet to become a owner and the title of the property will be on your name only after the registered sale deed is executed in your name by the seller/builder. 

Since this is not the sale of immovable property i.e., it is not an income out of sale of capital property, the income derived out of this transaction can be treated as an income through other sources, hence it will not attract capital gains tax.

you would be required to pay the income tax for your total income which will include this income also.

As you have not purchase the property by a registered sale deed, you can demand return of GST amount paid by you from the builder, who will in turn direct the buyer to bear it.  

No it will not be applicable again but capital gain may be applicable 

Dear Client,  

Residential properties covered in the affordable housing segment will be subject to a 1% GST charge without input tax credit. 12% GST is applied on real estate for under-construction properties. Completed properties are not subject to GST when they are sold. An 18% tax rate is applied to the sale of freshly built or under construction commercial properties based on the property's worth. The developer or constructor of the commercial property is subject to this tax, which they must submit to the government for payment. Capital gains on the sale of real estate are subject to a 20% tax. The entire tax outlay for a net capital gain of Rs. 63,00,000 is Rs. 12,97,800. The amount of taxes that must be paid on this is substantial. Reinvesting the capital gains from the sale of a residential property is advised. You must buy a new property either a year before or two years after the sale in order to be eligible for this exemption under Section 54 of the Income Tax Act, 1961.