St Mary, Saffron Walden, is widely recognised as one of the outstanding buildings of Essex but the dating and patronage of its late medieval work is still poorly understood. This article lays out the evidence for the chronology of building work from the late 1430s up to the 1520s, encompassing the chancel, tower, porches, aisles, nave and clerestorey, based on an exceptionally long run of churchwardens’ accounts and a large amount of testamentary evidence. It also analyses the records of its financing and argues that the town’s leadership adopted several different financial models over the fifteenth century, gradually moving from a broad-based to an increasingly exclusive financial programme. Together these allow for the programme’s patronage to be reconceived as a delicate balance affected by the parish’s leadership between changing economic, social and cultural forces, and their shared ambitions for a spectacular parish church.