One manuscript of the complete poem survives and is kept in the British Museum. It was written down around 1000 AD by two West Saxon Christian scribes. In the course of the past thousand years, the original manuscript has been scorched by fire and parts are crumbling or faded. Hence, sections of the text have had to be recovered from translations for the first edition, by the Icelandic scholar Thorkeln in 1815.
The date when the stories were composed is unknown, probably somewhere in the period between 650 and 850 AD. Some of the language used implies that the poem had been previously copied over at least 200 years. The poem has one historical reference - the killing of Beowulf's liege lord in a raid on the Frisians - which took place in about 521 AD and therefore sets the earliest date for the composition as the late 6th century. Chickering (p247-248) argues that the earliest likely date is about the time of Bede (673-735 AD) and the latest is the period from ca. 790 to 830 AD when Viking attacks were becoming more prevalent.
Similarly, there is no certainty about where the poem was composed. Almost any Anglo-Saxon kingdom is a possible location, depending on the grounds for selection - language, knowledge of Scandinavian geneology, description of objects, apparent compliments to named kings. As summarised by Chickering (p248 to 249) none of the arguments is particularly convincing. All seem to depend on a view of the Anglo-Saxon and Viking worlds that exaggerates the differences between tribal kingdoms and cultures.
Questions as to whether there can be considered to be one Beowulf poet and whether the original was a written or oral product seem irrelevant, imposing modern ideas of individual authorship and finished texts on communal and improvisatory forms of artistic expression. Chickering (p246) suggests that the story of Beowulf was seen mainly as a fabulous monster story, at the time when it was recorded. No other Anglo-Saxon sources refer to it.
Beowulf, A Dual Language Edition,(date uncertain),translated by Chickering, H D, Jr, Doubleday
A History of the English church and people, , translated by Sherley-Price, L, 1955, Penguin