Recesses in the rectangular tablets would originally be filled with blackened beeswax, which would have been written in using a stylus, and while the wax has not survived the writing sometimes went on to the wood and can be deciphered.
Sophie Jackson, archaeologist and director at independent charitable company Museum of London Archaeology (MOLA), which led the dig, said: "We always had high high hopes for the Bloomberg dig, situated in the heart of the Roman and modern city and with perfect wet conditions for the survival of archaeology, but the findings far exceeded all expectations.
"The writing tablets are truly a gift for archaeologists trying to get closer to the first Roman Britons."
Deciphering the tablets has revealed they include the earliest dated handwritten document in Britain, a financial record with the date of January 8, 57 AD.
Another tablet has been archaeologically dated to 43-53 AD, the first decade of Roman rule in Britain, and there is one containing the earliest ever reference to London in around 65-80 AD, 50 years before Roman historian Tacitus cites the city in his Annals.
One tablet is a contract from October 21, 62 AD, to bring "twenty loads of provisions" from Verulamium - modern day St Albans, Hertfordshire - to London, a year after the revolt by Iceni queen Boudica.
Experts said the contract reveals the rapid recovery of Roman London after it was burned in the Boudican revolt.
The writing tablets are truly a gift for archaeologists trying to get closer to the first Roman Britons
The names of nearly 100 people, from a cooper, brewer and judge to soldiers, slaves and freemen, found in the collection show the new city was inhabited by businessmen and soldiers.
Oxford University classicist and cursive Latin expert Roger Tomlin, who deciphered and interpreted the tablets, said: "The Bloomberg writing tablets are very important for the earliest history of Roman Britain, and London in particular.
"I am so lucky to be the first to read them again, after more than 19 centuries, and to imagine what these people were like, who founded the new city of London."
After they were excavated, the tablets were kept in water before being carefully cleaned and treated with a waxy substance to replace some of the water content and then freeze dried.
More than 700 artefacts from the excavation will go on display next year in an exhibition space in the new Bloomberg building, including the earliest dated writing tablet.
Bloomberg founder and owner Michael Bloomberg said: "As a company that is centred on communications - of data, information, news and analysis - we are thrilled that Bloomberg has been at the core of a project that has provided so much new information about London's first half-century."