Multiyear Procurement (MYP) and Block Buy Contracting in Defense Acquisition: Background and Issues for Congress [Updated October 15, 2020] [open pdf - 1MB]
From the Summary: "Multiyear procurement (MYP) and block buy contracting (BBC) are special contracting mechanisms that Congress permits the Department of Defense (DOD) to use for a limited number of defense acquisition programs. Compared to the standard or default approach of annual contracting, MYP and BBC have the potential for reducing weapon procurement costs by a few or several percent. Under annual contracting, DOD uses one or more contracts for each year's worth of procurement of a given kind of item. Under MYP, DOD instead uses a single contract for two to five years' worth of procurement of a given kind of item without having to exercise a contract option for each year after the first year. DOD needs congressional approval for each use of MYP. There is a permanent statute governing MYP contracting--10 U.S.C. 2306b. Under this statute, a program must meet several criteria to qualify for MYP."
CRS Report for Congress, R41909
Congressional Research Service: https://crsreports.congress.gov/