The spelling conventions for dental fricatives in Anglic languages (Scots and English) have a rich and complex history. However, the various – often competing – graphemic representations (⟨þ⟩, ⟨ð⟩, ⟨y⟩ and ⟨th⟩, among others) eventually settled on one digraph, ⟨th⟩, for all contemporary varieties, irrespective of the phonemic distinction between /ð/ and /θ/. This single representation is odd among the languages’ fricatives, which tend to use contrasting graphemes (cf. ⟨f⟩ vs. ⟨v⟩ and ⟨s⟩ vs. ⟨z⟩) to represent contrastive voicing, a sound pattern that emerged nearly a millennium ago. Close examinations of the scribal practices for English in the late medieval period, however, have shown that northern texts had begun to develop precisely this type of distinction for dental fricatives as well. Here /ð/ was predominantly represented by ⟨y⟩ and /θ/ by ⟨th⟩ (Jordan, 1934; Benskin 1982). In the late 15th and early 16th centuries, this “Northern System” collapsed, due to the northward spread of a London-based convention using exclusively ⟨th⟩ (Stenroos, 2004). This paper uses a rich body of corpus evidence for 15th-century Scots to show that, north of The North, the phonemic distinction was more clearly mirrored by spelling conventions than in any contemporary variety of English. Indeed, our data for Older Scots local documents (1375-1500) shows a pattern where ⟨y⟩ progressively spreads into voiced contexts, while ⟨th⟩ recedes into voiceless ones. This system is traced back to the Old English positional preferences for ⟨þ⟩ and ⟨ð⟩ via subsequent changes in phonology, graphemic repertoire and letter shapes. An independent medieval Scots spelling norm is seen to emerge as part of a developing, proto-standard orthographic system, only to be cut short in the sixteenth century by top-down anglicisation processes.