The Income Tax Assessment Act 1936 (Cth) is an Act of the Parliament of Australia. It is one of the main statutes under which income tax is calculated. The Act is gradually being rewritten into the Income Tax Assessment Act 1997, and new matters are generally now added to the 1997 Act. The reason for rewriting the act is that amendments over the years have made it thousands of pages long, and very complex. Amendments have also created subsection upon subsection.