The Reserve Forces Act 1937 (1. Edw. VIII & 1. Geo. VI, c. 17) was an Act of Parliament of the Parliament of the United Kingdom. It allowed "Class A" British Army reservists to be called up for active service during their first five years after leaving the Army. Accordingly, the 1937 Act extended the period of liability to any point during the first five years in the first-class reserve, or the unexpired period of his original enlistment. However, this was still voluntary, and the reservist had to agree in writing to be liable.