The Self-denying Ordinance was passed by the English Parliament on 3 April 1645. All members of the House of Commons or Lords who were also officers in the Parliamentary army or navy were required to resign one or the other, within 40 days from 3 April 1645.

The New Model Army or New Modelled Army was a standing army formed in 1645 by the Parliamentarians during the First English Civil War, then disbanded after the Stuart Restoration in 1660. It differed from other armies employed in the 1639 to 1653 Wars of the Three Kingdoms in that members were liable for service anywhere in the country, rather than being limited to a single area or garrison. To establish a professional officer corps, the army's leaders were prohibited from having seats in either the House of Lords or House of Commons. This was to encourage their separation from the political or religious factions among the Parliamentarians.