The Collaborative International Dictionary of English v.0.48:

Annats \An"nats\, Annates \An"nates\, n. pl. [See Ann.] (Eccl.
   Law)
   The first year's profits of a spiritual preferment, anciently
   paid by the clergy to the pope; first fruits. In England,
   they now form a fund for the augmentation of poor livings.
   [1913 Webster]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

ANNATES, ecc. law. First fruits paid out of spiritual benefices to the pope,
being, the value of one year's profit.