Trinoda necessitas ("three-knotted obligation" in Latin) is a term used to refer to a "threefold tax" in Anglo-Saxon times. Subjects of an Anglo-Saxon king were required to yield three services: bridge-bote (repairing bridges and roads), burgh-bote (building and maintaining fortifications), and fyrd-bote (serving in the militia, known as the fyrd). Rulers very rarely exempted subjects from the trinoda necessitas, because these services were the lifeblood of an Anglo-Saxon kingdom. After the Norman Conquest, exemptions from the trinoda necessitas became more common.
The term "trinoda necessitas" was rarely used in Anglo-Saxon times: its only known use is in a grant of land near Pagham, Sussex from King Cædwalla of Wessex to Saint Wilfred. The Wilfred grant used the term trimoda (Latin for "triple"); trinoda (Latin for "triple-knotted") was an error introduced by John Selden in 1610.
Instead of the term "trinoda necessitas", it was common for Anglo-Saxon land grants to spell out the three obligations individually. For example, the land grant of Æthelberht of Kent to a thegn in 858 was free of obligation, except explicitly for military service, bridge repair, and fortification.
See also
- History of English land law
References

![[C] Necessitas Custom by Verridith on DeviantArt](https://images-wixmp-ed30a86b8c4ca887773594c2.wixmp.com/f/2918ddf2-37ca-4544-82de-7b54beca3a08/dgxjezp-376d2f07-1e49-43f9-8b30-b9883cc2905c.png/v1/fill/w_1920,h_1783/_c__necessitas_custom_by_verridith_dgxjezp-fullview.png?token=eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJzdWIiOiJ1cm46YXBwOjdlMGQxODg5ODIyNjQzNzNhNWYwZDQxNWVhMGQyNmUwIiwiaXNzIjoidXJuOmFwcDo3ZTBkMTg4OTgyMjY0MzczYTVmMGQ0MTVlYTBkMjZlMCIsIm9iaiI6W1t7ImhlaWdodCI6Ijw9MTc4MyIsInBhdGgiOiJcL2ZcLzI5MThkZGYyLTM3Y2EtNDU0NC04MmRlLTdiNTRiZWNhM2EwOFwvZGd4amV6cC0zNzZkMmYwNy0xZTQ5LTQzZjktOGIzMC1iOTg4M2NjMjkwNWMucG5nIiwid2lkdGgiOiI8PTE5MjAifV1dLCJhdWQiOlsidXJuOnNlcnZpY2U6aW1hZ2Uub3BlcmF0aW9ucyJdfQ.giod-nYJNRFyK0qfolmou7gIbWRoChsMD6AAf8-mibk)

