A unit's Decommission bonus (known as Bounty value in game-data files, and here referred to as Refund amount) is an amount of resources that the player may gain when non-Hero and non-Siege units are no longer wanted. This refund amount will increase as the unit's level increases, but varies for different units of different factions.
Easterlings being decommissioned at Helm's Deep
Decommissioning is done by selecting unwanted infantry and right-clicking on any of the player's Fortresses or, if the player is based in the stronghold of a Fortress-map, by right-clicking on the Keep. The decommissioning feature is ideal for when the player's command point amount consists too much of battalions at low health who cannot heal, as is the case with units of all Evil factions.
As each decommissioned individual enters, a very minimal refund to the player's resources will be shown.
For the forces of Mordor alone, there is one special condition to refund-locations: Orc archers and warriors can be decommissioned at a Slaughter House, for a larger refund than if sent elsewhere.
In The Battle for Middle-earth II, Men of the West and the Dwarves have ways of increasing their units' decommission bonus, through the construction of Hall Expansions and Dormitories, each of which increase the bonus by 25%.