This article investigates differences between Scottish Standard English (SSE) and Southern British Standard English (SBSE) in the semantic domain of strong obligation. Focusing on the modal verbs must, have to, need to and (have) got to, we use new corpus material from nineteen written and spoken genres in the Scottish component of the International Corpus of English (ICE-SCO) and corresponding texts from ICE-GB. Data are analysed using a mixed-effect multinomial regression model to predict the choice of verb. Language-internal factors include mode of production (written/spoken), grammatical subject (first/second/third person) and source of obligation (objective/subjective). Our results show that, as previous research suggests, SSE is much more likely to employ need to for the expression of strong obligation, and less likely to employ must and (have) got to. This general pattern remains essentially unaffected by language-internal factors. To account for our findings, we draw on the sociologically motivated process of democratisation and the language-internal process of grammaticalisation.