FIFO rule for dematerialised securities determines transfer date and holding period for capital gains computation. Determination of date of transfer and period of holding for dematerialised securities under section 45(2A) requires application of the FIFO method to units credited to a demat account; FIFO is confined to dematerialised holdings, is applied accountwise across multiple demat accounts, and entries of dematerialised physical certificates take their place in the FIFO sequence based on the date of credit to the account. When a sale can be specifically linked to an earlier purchase by contract notes, the general rules for date of transfer and period of holding apply.