Year of Tax Liability in case of Cap Gains

Mr. A sold his ancestral property in FY 18-19 (through sale deed); however, the consideration is in the form of Post Dated Cheques (all are dated FY 19-20).
The possession is given to the buyer.
There is a clause in the sale deed which says - "If any of the post dated cheque gets dishonored, this deal will be cancelled."

My question is in which year the tax liability gets attracted - FY 18-19 (wherein no consideration is received) or FY 19-20 (on the ground that if any of the cheques got dishonored, the deal will be cancelled and hence, this transfer will be completed only on the realisation of the last cheque i.e. in FY 19-20)

Thanks in advance!