A typical share sale agreement (SPA) takes effect on signing. Closing, when the buyer and the seller exchange money and title to the shares, usually comes later, once conditions have been met. One might expect tax on the sale to be imposed when the shares are sold, that is, at closing. But where a foreign enterprise with no permanent establishment (Foreign Seller) in Vietnam sells shares in an unlisted Vietnamese company to a resident buyer, Article 5.2(a) of Circular 20/2026 provides that revenue is taxed when the initial capital-transfer contract takes effect. On the face of that Article, the SPA can be that contract, and signing can be when it takes effect. The fact that closing has not yet occurred might not, by itself, defer the tax. Until Circular 20/2026, that was not so.