This paper aims to examine two elements, u and a, in the Amis left periphery, showing that u and a are highly relevant to finiteness and to the tense, aspect, and mood (TAM) of the embedded clause, and are influenced by their other functions. Specifically, Amis u is originally a noun marker, and as a complementizer it tends to occur with other deverbalized devices. Amis a is reported as the future marker in another dialect, and this function may influence the embedded clause that it introduces to very often be an irrealis one. This paper proposes that u is a Finite Head (Fin), while a is either an irrealis Fin or a defective Modal-Aspectual (Mod-Asp). This study also concludes that, in Amis, there are only two levels of complementation: finite Complement Phrase (CP) and infinite Mod-AspP, which is less diverse than in English. This explains why different types of Amis complement clauses are often structured similarly.