"Do the needful" is an archaic expression which means "do that which is necessary", with the respectful implication that the other party is trusted to understand what needs doing without being given detailed instruction.

The expression is now current mainly in South Asian English (Indian

Indian English

Indian English is an umbrella term used to describe dialects of the English language spoken primarily in the Republic of India.As a result of British colonial rule until Indian independence in 1947 English is an official language of India and is widely used in both spoken and literary contexts...

, Pakistani

Pakistani English

Pakistani English is the term used to describe the English language as spoken in Pakistan. Pakistani English is slightly different in respect to accent and spellings of some words.-History:...

 and Sri Lankan

Sri Lankan English

Sri Lankan English is the English language as spoken in Sri Lanka.The earliest English speakers in present-day Sri Lanka date back to the days of the British Empire, the era of Royal Navy dominance, and the British colonial presence in South Asia....

). The expression was current in both British

British English

British English, or English , is the broad term used to distinguish the forms of the English language used in the United Kingdom from forms used elsewhere...

 and American English

American English

American English is a set of dialects of the English language used mostly in the United States. Approximately two-thirds of the world's native speakers of English live in the United States....

 well into the early 20th century. In later years it was sometimes used as parody example of contemporary South Asian English.

The Oxford English Dictionary

Oxford English Dictionary

The Oxford English Dictionary , published by the Oxford University Press, is the self-styled premier dictionary of the English language. Two fully bound print editions of the OED have been published under its current name, in 1928 and 1989. The first edition was published in twelve volumes , and...

lists examples of usage from 1709 (Richard Steele

Richard Steele

Sir Richard Steele was an Irish writer and politician, remembered as co-founder, with his friend Joseph Addison, of the magazine The Spectator....

 in the Tatler

Tatler

Tatler has been the name of several British journals and magazines, each of which has viewed itself as the successor of the original literary and society journal founded by Richard Steele in 1709. The current incarnation, founded in 1901, is a glossy magazine published by Condé Nast Publications...

), 1771 (Samuel Foote

Samuel Foote

Samuel Foote was a British dramatist, actor and theatre manager from Cornwall.-Early life:Born into a well-to-do family, Foote was baptized in Truro, Cornwall on 27 January 1720. His father, John Foote, held several public positions, including mayor of Truro, Member of Parliament representing...

 in Maid of Bath), 1821 (Maria Edgeworth

Maria Edgeworth

Maria Edgeworth was a prolific Anglo-Irish writer of adults' and children's literature. She was one of the first realist writers in children's literature and was a significant figure in the evolution of the novel in Europe...

 in a letter), 1831 (Walter Scott

Walter Scott

Sir Walter Scott, 1st Baronet was a Scottish historical novelist, playwright, and poet, popular throughout much of the world during his time....

 in his journal), 1929 (I. Colvin in his Life of Dyer), and 1992 (Jeff Torrington

Jeff Torrington

Jeff Torrington was a novelist from Glasgow in Scotland.His novels draw on the changing face of modern Scotland. Swing Hammer Swing was set during the demolition of the old Gorbals. It took 30 years to write. The Devil's Carousel drew on the decline of a fictionalised version of the...

in Swing Hammer Swing!), the last likely used humorously.