The Indian spot-billed duck was described by the naturalist Johann Reinhold Forster in 1781 under its current binomial name Anas poecilorhyncha.

[5] A 2014 study, however, shows that there is discordance between the phylogenies obtained using nuclear DNA sequences; the Indian spot-bill appears to be closer to the Laysan and Hawaiian ducks and forming a sister clade to the New World and Old World mallards and the Mexican, American black and mottled ducks.

There is significant hybridization between Old World mallards and eastern spot-billed ducks, leading to a closeness in their mitochondrial DNA that alters the apparent phylogenies.

[8][11][12] This duck is around the same size as a mallard and has a scaly patterned body with a green speculum bordered by white.

At rest the white stripe stands out and the long neck and the bill with yellow tip and orange red spots at the base are distinctive in the nominate subspecies.

The wings are whitish with black flight feathers below, and from above show a white-bordered green The male has a red spot on the base of the bill, which is absent or inconspicuous in the smaller but otherwise similar female.

They tend to avoid very large patches of open water and prefer medium-sized wetlands with vegetation cover.

The northernmost populations have expanded their range northwards by more than 500 km since the early 20th century, possibly in reaction to global warming.

[18] It is a bird of freshwater lakes and marshes in fairly open country and feeds by dabbling for plant food mainly in the evening or at night.

[28] In southern India, a method of hunting involved using floating bundles of rushes on which the hunters lay in wait.