The gain waits for the completion certificate
Ordinarily, handing over land is a transfer that triggers capital gains at once. A joint development agreement gets special treatment for an individual or HUF landowner. Under Section 45(5A), the gain on giving your land into the project is charged only in the year the competent authority issues the completion certificate for the whole or part of the project, not in the year you sign the agreement. So you are not taxed years ahead of receiving anything.
When that year comes, the sale value is computed as the stamp-duty value of your share of the finished project, the flats allotted to you, on the completion-certificate date, plus any cash the builder paid you along the way. Two conditions matter: the benefit is for individuals and HUFs, not companies or firms, and the development agreement must be registered. An NRI individual landowner qualifies.
The trap that loses the deferral, and the TDS
The one thing that breaks the deferral is selling early. If you transfer your share in the project, the flats coming to you, on or before the date the completion certificate is issued, Section 45(5A) no longer applies and the gain is taxed in the ordinary way in the year of that transfer. So a landowner who flips their allotment before the project completes gives up the timing benefit; holding to completion preserves it.
On the cash the builder pays you, the deduction of tax matters. The 10% rate under Section 194-IC applies only where the landowner is a resident; because you are a non-resident, the cash consideration is instead subject to TDS under Section 195. There is no TDS on the flats themselves, the in-kind part. As with any NRI sale, a Form 13 lower-deduction certificate can bring the withholding on the cash down to your real tax rather than a flat rate on the gross.
The flats you receive, and selling them later
The flats you get out of the project are a fresh asset in your hands. Under Section 49(7), their cost of acquisition is the same deemed value that was used as your sale consideration under Section 45(5A), the stamp-duty value at completion plus cash, so there is no double counting. Their holding period runs from the completion or allotment date, not from when you first owned the land.
When you later sell one of those flats, it is an ordinary immovable-property sale: long-term if held more than twenty-four months, taxed for an NRI at the flat 12.5% with no indexation for sales on or after 23 July 2024 (Section 112). The resident-only option of 20% with indexation does not apply to you. A practising CA maps the whole arc, the deferred gain at completion, the TDS on the cash, and the cost and rate on any later flat sale.