What is a handicap allowance and how is it used?
Why am I not receiving all my handicap strokes in a tournament?
Handicap Allowances are designed to provide equity for players of all levels of ability in all formats of play. These percentages (less than 100% of the player's Course Handicap) are applied in the final step in calculating the player's Playing Handicap for use in competition. The final decision for the Handicap Allowance to be applied is for the Committee in charge of the competition to make. Most often, allowances are used in team events. The USGA recommendations can be found here -
Appendix C: Handicap Allowances, Rules of Handicapping