Rare drawings by William Blake and Joshua Reynolds and a number of collections of letters have passed into public hands.
Letters by Graham Greene and TS Eliot are amongst the haul
The works, which were privately owned, have been accepted by the government instead of inheritance tax.
The haul is worth £13m and includes letters from Henry Moore, Barbara Hepworth, Graham Greene and TS Eliot.
The drawings include Reynolds' Cupid and Psyche, worth £420,000 and a pencil drawing by Blake of Isaac Newton.
All of the work was handed over under the Acceptance in Lieu Scheme (AIL), which allows inheritance tax bills to be settled with important art works and archives to an equivalent value.
The Museums, Libraries and Archives Council says the collections of letters - like those of poet Kathleen Raine - are particularly important, as people now communicate by telephone, e-mail and text rather than letter.
Chairman Mark Wood said: "In five years, 140 offers, between them worth £140m have been completed resulting in many hundreds of items going to public collections.
"The range of objects is breathtaking, from an ancient Egyptian bronze to 20th Century political archives.
"Schemes such as this are absolutely essential if British museums are to retain their unique international status."
Blake's drawing of Isaac Newton is the only known study for one of his most famous works and the two other drawings handed over are also viewed as important.
Other works include Still Life with Lemons and Oranges by Luis Melendez and Christopher Wood's Zebra and Parachute, which were given to settle tax bills of £1m and £245,000 respectively.