The personnel you'll work with in your government contracts are much more closely regulated than are their counterparts in the private sector. The Federal Acquisition Regulation (FAR) is fairly strict on the level of authority each contracting officer has. Here's a quick rundown of the different agency personnel commonly associated with a government contract.

Contracting Officer
Of all government personnel, only a Contracting Officer has the authority to enter the government into a binding contract. He or she will be the one to sign the final contract agreement, and only a Contracting Officer has the power to change the terms of the contract.

From part 1.602-1 of the FAR:
"(a) Contracting officers have authority to enter into, administer, or terminate contracts and make related determinations and findings. Contracting officers may bind the Government only to the extent of the authority delegated to them. Contracting officers shall receive from the appointing authority…clear instructions in writing regarding the limits of their authority. Information on the limits of the contracting officers' authority shall be readily available to the public and agency personnel.
(b) No contract shall be entered into unless the contracting officer ensures that all requirements of law, executive orders, regulations, and all other applicable procedures, including clearances and approvals, have been met."

The Contracting Officer's authority is derived from a warrant, which must be displayed. Some warrants give unlimited contracting authority, while others may limit the CO to certain dollar amounts or supplies. It's worth nothing that although delegates of the Contracting Officer may also bear titles including "Contracting Officer," the authority granted by the warrant cannot be delegated.

Procuring Contracting Officer
The Procuring Contracting Officer has ultimate responsibility for the government's side for contract execution, regardless of whatever additional support team may be outlined in the contract. The PCO is responsible for overseeing the contract from start to finish, including drawing up the procurement package, RFP, and contract award, as well as administration during the contract's lifecycle. He or she will ensure that all laws are being followed, such as employment fair treatment practices.

Administrative Contracting Officer
This officer, as the title suggests, administers day-to-day activities following the contract award. The ACO may not have official Contracting Officer status but may be a delegate of the Contracting Officer.

Termination Contracting Officer
Should the contract need be concluded early, whether for convenience or default, the Termination Contracting Officer will be called in to negotiate the terms of the termination with the contractor.

Contracting Officer's Representatives
Appointed by the CO/PCO, Contracting Officer's Representatives serve as the go-between for the CO and the contractor. The COR is there to monitor the contract, provide guidance and clear up any miscommunications. A COR may also set responsibilities and limits as dictated by the CO. Often, the COR for a particular contract is recommended by the program manager, but the COR ultimately reports to the Contracting Officer. Many agencies require Contracting Officer Representatives to complete a training course and ongoing education. The COR's authority applies only to the project at hand.

As a government contract manager, it's important to remember that anyone other than these contracting officials does not have the authority to change the project in any way. Any changes suggested by another party should be cleared with the PCO or ACO first – the contractor will be liable for the time/expense taken by any unauthorized action.