Can a micro purchaser sign a contractor's proposal for $1,200.00? The amount for the service is within the micro purchaser dollar purchase amount.
A question you need to address is "what am I signing?" The Department of Defense Government Purchase Card (GPC) Review Checklist and Certification (Item 8) has an item for review that states: "There were no purchases that required the Cardholder to sign a document agreeing to terms and conditions." If the proposal includes contractor terms and conditions then it is outside your authority.
A signature on a proposal is an obligation for the U.S. Government and is an authority vested in the Contracting Officer as defined in FAR 2.101:
“Contracting officer” means a person with the authority to enter into, administer, and/or terminate contracts and make related determinations and findings. The term includes certain authorized representatives of the contracting officer acting within the limits of their authority as delegated by the contracting officer. “Administrative contracting officer (ACO)’’ refers to a contracting officer who is administering contracts. “Termination contracting officer (TCO)” refers to a contracting officer who is settling terminated contracts. A single contracting officer may be responsible for duties in any or all of these areas. Reference in this regulation (48 CFR Chapter 1) to administrative contracting officer or termination contracting officer does not--
(1) Require that a duty be performed at a particular office or activity or
(2) Restrict in any way a contracting officer in the performance of any duty properly assigned.
As you can see, the definition includes "certain authorized representatives of the contracting officer acting within the limits of their authority as delegated by the contracting officer." This delegation, if so granted, would be expressly identified and provided for. A Government Purchase Cardholder's authority is identified on delegation letter or if used, a DD Form 577, Appointment/Termination Record - Authorized Signature. Unless specified upon appointment, the authority to sign an obligation will remain a contracting officer responsibility.
See also, FAR 4.101 which states:
Only contracting officers shall sign contracts on behalf of the United States. The contracting officer’s name and official title shall be typed, stamped, or printed on the contract. The contracting officer normally signs the contract after it has been signed by the contractor. The contracting officer shall ensure that the signer(s) have authority to bind the contractor (see specific requirements in 4.102 of this subpart).
A good reference is the DEPARTMENT OF DEFENSE GOVERNMENT CHARGE CARD GUIDEBOOK FOR ESTABLISHING AND MANAGING PURCHASE, TRAVEL, AND FUEL CARD PROGRAMS, found here: https://www.acq.osd.mil/dpap/pdi/pc/docs/DoD_Govt_Charge_Card_Guide_10_1_2017%20-%20Jan_24_Rev.pdf
At A.1.2.2 GPC PURCHASING STEPS; there is a comprehensive step-by-step process for making purchases. Regarding your question, see paragraph b) "Mandatory: Determine whether the requirement can be met within the limits specified in the CH’s Delegation of Authority Letter." Which takes us back to the original answer regarding what your specified delegation of authority states.