The Formula was folded into the Book of Concord in 1580, alongside the three ecumenical creeds, both of Luther's catechisms, the Augsburg Confession and its Apology, and the Smalcald Articles, giving Lutheranism a single bound collection of confessional documents comparable to what the Reformed churches assembled piecemeal over the following century.
Around eight thousand clergy and officials across the German territories signed the Book of Concord in the years around 1580, an unusually broad subscription for the period, though several important territories, including electoral Brandenburg for a time and the city of Bremen, refused it and kept their churches on the Augsburg Confession alone. That split has outlasted the sixteenth century.
Confessional Lutheran bodies, including most Lutheran state churches and the conservative American synods, still require office bearers to subscribe to the whole Book of Concord as a correct exposition of Scripture. Other Lutheran churches, particularly those shaped by nineteenth century revivalism or twentieth century ecumenism, receive only the Augsburg Confession and Luther's Small Catechism as binding and treat the Formula of Concord as a historical document rather than a present standard, which is why a visitor cannot assume from the name Lutheran alone how much of the 1580 book a given congregation actually holds.