This article examines four cases concerning the application of section 10(1)(g) of Singapore’s Income Tax Act – which imposes tax on gains or profits of an income nature that do not fall within any of the preceding paragraphs of section 10(1) – to profits derived from the sale of shares and real property. While the GBU case, decided in 2017, has endorsed the narrower scope of the so-called IB proposition in applying section 10(1)(g), the author submits that the conceptual distinction between that provision and section 10(1)(a), which taxes gains or profits from a trade, business, profession or vocation, remains unclear.