Instruments subject to the made affirmative procedure are signed into law before being laid in Parliament. They either come into force before being laid, or on approval by Parliament. The approval period for instruments that come into force before being laid starts when they are signed into law. The length of this period is defined in the parent Act. If either House does not approve an instrument which came into force before being laid, the instrument is stopped. Instruments concerning taxation are not laid in the Lords and only require the approval of the Commons.