The Company Store ploy is a long-term gambit by the employer of a mercenary unit (or individual mercenary) to financially bankrupt the unit in question. The intended goal is to force the mercenaries into either selling most, often all, of their equipment (especially 'Mechs) to the employer to pay off their accumulated debts, or to enter the employer's service permanently. Several states maintain military units that used to be independent mercenary commands who were taken over in this way.
Historically, the Draconis Combine and the Federated Suns are known to implement Company Store policies more than other Successor States, but all powers use the Company Store concept to some extent.
Almost all mercenary units require support from the employer in the form of space transportation, repairs and often even simple maintenance as well as basic supplies such as ammunition, spare parts, fuel, food and other consumables. These services are paid for by the mercenary outfit and under normal circumstances the regular pay is more than enough to cover the bills. A side-effect is that the support and the supplies have to follow regular channels. This means that requests are handled by the bureaucracy and provided through regular supply lines.
In a Company Store scenario, the employer typically offers the mercenaries direct access to the military's quartermaster service on a cash-and-carry basis, the employer often making this more appealing by offering either discounted rates or an increase in pay to offset any price difference on purchases of House supplies and services, or in more blatant attempts offers of deferred payment. The catch is that the price of the supplies and services is also increased, whether openly or surreptitiously, to the point where the unit's regular income is too small to pay the costs. This forces the unit to undertake supplementary contracts in order to cover its debts. Such missions typically consist of dangerous raids, which often encounter fierce opposition, resulting in heavy combat damage which requires more costly supplies (mainly replacing expended munitions and repairing damage) and repairs, thus incurring even more debt. This vicious cycle continues until the debt becomes overwhelming, at which point the mercenaries are forced to renegotiate their contract to pay off their debts. The new contracts are heavily biased towards the employer; more often than not the mercenary unit is either permanently bound to that employer alone, or in the most egregious cases outright absorbed into the employer's regular armed forces. Some mercenaries are sometimes simply stripped of their equipment and left destitute.   
The tactic of the Company Store is most successful when applied to smaller and underfunded mercenary commands. Larger or more successful commands are known to sell off elements of their TO&E, such as DropShips and JumpShips, to avoid or pay off such debts and stave off being absorbed. The only other alternative is to break contract and to flee the inevitable punishment, either suffering the consequences with the Mercenary Review Board or deserting and becoming pirates. For this reason even employers desperate to force mercenaries into permanent service favor subtlety rather than blatant gouging, ever mindful that there is fine line between permanently ensnaring a command and driving them into the arms of their enemies.  
- One famous example of "company store treatment" is the Paul Bunyan Regiment once employed by House Kurita, which was one of a number of units who accepted increased pay in exchange for access to DCMS procurement channels in 2822, but was systematically undermined by price-hikes and the need to supplement their income with secondary raiding contracts (which consumed more supplies and increased their debts). In 2825, the situation came to a head. While the Paul Bunyan Regiment was stationed on Zlatous, the DCMS outright stopped their pay, citing a need to cover their debts. In response, the regiment mutinied, seizing several warehouses to obtain food and other necessities. Declaring them a rogue unit, the DCMS destroyed the regiment's DropShips and deployed the 5th and 9th Galedon Regulars. After two months of fierce fighting the majority of the Paul Bunyan Regiment was destroyed. A handful of survivors managed to escape in a captured DCMS DropShip, fleeing into the Periphery. The DCMS learned from this response to make their future "company store" efforts more subtle, taking longer to bear fruit but also making it harder for units to realize what was happening.  
- At one point in their employment by House Kurita, Wolf's Dragoons suspected that Warlord Grieg Samsonov was attempting to use the Company Store gambit as part of a campaign to seize direct control of the Dragoons.
- The Northwind Highlanders nearly became victims to a Company Store attempt by the Federated Suns in 3057. Adamant defense of their independence and the political instability caused by Operation Guerrero led to armed conflict that ultimately made Northwind a free state.
- House Kurita (sourcebook), p. 62 "History - Second Succession War - Snakes and Sneaks"
- Handbook: House Kurita, p. 45 "History of the Nation - The Second Succession War - Mercenaries and the Dragon"
- Combat Manual: Mercenaries, p. 36 - "The Company Store"
- Mercenary's Handbook, p. 12 "The Business of War - Consumables"
- Mercenary's Handbook, p. 28 "Mercenary Concerns - The Company Store"