Prior to beginning a project, a software development contract is signed between us stating:

169. Parties shall deem all Deliverables created by
TPC as "works made for hire" as defined under the 
Copyright Law of the United States of America
(edition of June 2003)

Reference to Copyright Law of the United States of America means that Deliverables created for you by TPC are "Works Made For Hire" as defined in the Law:

Copyright Law of the United States, par. 201:
(b) Works Made for Hire.-In the case of a work made
for hire, the employer or other person for whom
the work was prepared is considered the author for
purposes of this title, and, unless the parties have
expressly agreed otherwise in a written instrument
signed by them, owns all of the rights comprised
in the copyright.

Thus, Deliverables and the Intellectual Propery Rights (IPR) for them are transferred to you when the project is closed, plus the Acceptance Statement is signed and the final payment is processed.