Acquisition Category (ACAT): Levels, Thresholds, and MDA Role

An Acquisition Category, or ACAT, is the Department of Defense’s classification that sorts every program on the Major Capability Acquisition pathway into one of three tiers based on projected cost, and the tier determines who serves as the decision authority and how much oversight the program receives.¹ The top tier, ACAT I, captures programs with research and development costs above $1 billion or total procurement above $4.5 billion in fiscal year 2024 constant dollars.² Below that sit ACAT II for major systems and ACAT III for everything else. The framework exists so a billion-dollar fighter jet doesn’t get the same light-touch management as a subsystem upgrade.

The Three ACAT Levels and Their Thresholds

ACAT I is reserved for Major Defense Acquisition Programs. A program qualifies when its estimated total research, development, test, and evaluation spending exceeds $1 billion, or total procurement exceeds $4.5 billion, both measured in fiscal year 2024 constant dollars.² The Secretary of Defense can also designate a program as an MDAP regardless of cost. These are the programs that draw the most congressional attention and consume the largest share of the defense budget. The F-35 Joint Strike Fighter and the Columbia-class ballistic missile submarine sit here.

ACAT II covers programs below the ACAT I line that still count as “major systems” under Title 10. DoDI 5000.85 places the floor at more than $200 million in research and development or more than $920 million in total procurement, both in fiscal year 2020 constant dollars.¹ Oversight sits with the Component Acquisition Executive rather than with centralized Pentagon leadership.

ACAT III catches everything that doesn’t meet the ACAT II thresholds and hasn’t been designated a major system by the Milestone Decision Authority.¹ These programs often involve equipment modifications, specialized tools, or subsystem work that supports larger platforms. Documentation is lighter. That isn’t the same as unmanaged, though. ACAT III programs still follow the core acquisition process.

Because the thresholds are set in constant-year dollars, inflation alone can’t push a program up a tier. Only real growth in scope or capability moves the needle.

ACAT I Sub-Designations: ID, IB, and IC

Not every ACAT I program answers to the same official. The top tier splits into three sub-designations based on who serves as the Milestone Decision Authority:¹

ACAT ID programs are overseen by the Defense Acquisition Executive, a role held by the Under Secretary of Defense for Acquisition and Sustainment. The Pentagon’s senior acquisition official personally shepherds each milestone decision.
ACAT IB programs still meet MDAP thresholds, but the decision authority is delegated one level down to the Service Acquisition Executive of the relevant military branch.
ACAT IC programs are overseen by the head of the DoD component or, if further delegated, the Component Acquisition Executive.

The distinction matters in practice. An ACAT ID designation routes every milestone decision through the Pentagon’s top acquisition office, which means more documentation, longer review cycles, and more stakeholders in the room than a program run at the service level.

How a Program Ends Up in a Category

Cost drives the initial classification. Analysts estimate total lifecycle spending for a program, separating research and development from procurement, and those projections get measured against the statutory and regulatory thresholds.

Cost isn’t the only lever. The Milestone Decision Authority can flag any program as “special interest,” which elevates its oversight regardless of the dollar estimates.¹ A program might earn that label because it involves sensitive technology, requires unusual coordination between services, or carries political significance.

Categories also aren’t permanent. When cost growth brings a program within 10 percent of the next higher ACAT level, the Milestone Decision Authority will consider recategorizing it.¹ A program tracking upward from ACAT II toward the $4.5 billion procurement line faces a real chance of being reclassified to ACAT I, with all the additional reporting that follows.

What the Milestone Decision Authority Actually Does

The Milestone Decision Authority, or MDA, is the official responsible for deciding whether a program moves to its next development phase. That role includes approving entry into each subsequent stage of the acquisition process along with accountability for cost, schedule, and performance outcomes.³

For ACAT I programs reaching Milestone A after October 2016, the default MDA is the Service Acquisition Executive of the military department managing the program. This was a shift from earlier practice, which centralized most MDAP decisions at the Pentagon. The Secretary of Defense can still designate an alternate MDA when cost, schedule, or performance risks justify more centralized control.⁴

Each milestone is a gate. Milestone C, for instance, is the decision point for entering production and deployment, and before granting approval the MDA has to verify that the production design is stable, developmental testing meets requirements, software is mature, manufacturing risks are manageable, costs fall within affordability limits, and full funding exists in the Future Years Defense Program.⁵ Missing any of those can block a program from moving forward, regardless of how much has already been spent.

Where ACAT Designations Don’t Apply

ACAT categories attach to the Major Capability Acquisition pathway, which is one of six pathways within the Adaptive Acquisition Framework.¹ Programs on other pathways operate under different oversight structures.

The Middle Tier of Acquisition is worth flagging. Programs using rapid prototyping or rapid fielding procedures under this pathway do not meet the statutory definition of a Major Defense Acquisition Program.¹ The exemption has limits: when a Middle Tier program is expected to exceed MDAP cost thresholds, it requires written approval from the Under Secretary of Defense for Acquisition and Sustainment before funds can be obligated.

Defense Business Systems use a separate scheme called Business System Categories. BCAT I covers systems with budget authority above $250 million over the Future Years Defense Program, BCAT II covers those above $50 million, and BCAT III captures the rest. Unlike standard ACATs, business systems don’t automatically drop when costs fall below a threshold. The MDA has to affirmatively decide to reclassify downward.⁶

What ACAT I Designation Triggers Beyond Oversight

The category label carries a set of legal obligations that follow the program throughout its life.

Independent Technical Risk Assessments

Before an ACAT I program can receive Milestone B approval or enter production, the Secretary of Defense must conduct or approve an independent technical risk assessment.⁷ The assessment identifies critical technologies or manufacturing processes that haven’t been demonstrated in a relevant environment. Independence is the point: program offices have an inherent incentive to present their technology readiness in the best possible light, and the assessment gives the decision authority evidence to delay a program that isn’t ready.

Nunn-McCurdy Cost Growth Controls

When an ACAT I program’s unit costs run away, Nunn-McCurdy provisions in Title 10 force the Department to act. The law defines two tiers of overrun measured against both the current and original baseline estimates:⁸

A significant breach is unit cost growth of at least 15 percent over the current baseline or 30 percent over the original.
A critical breach is unit cost growth of at least 25 percent over the current baseline or 50 percent over the original.

All figures are measured in constant base-year dollars. A significant breach obligates the Secretary of Defense to report to Congress on the increase, its causes, and corrective actions.⁹

A critical breach carries much heavier consequences. The law presumes the program should be terminated unless the Secretary personally certifies to Congress that it is essential to national security, that no less costly alternatives exist, that the revised cost estimates are reasonable, that the program outranks others that would lose funding to cover the overrun, and that its management structure can control future costs.¹⁰ All five must be met. Without certification, no appropriated funds can be obligated to major contracts on the program.⁹ In practice, most programs that trigger critical breaches get certified rather than terminated.

Congressional Reporting

ACAT I programs carry the heaviest reporting burden. For decades the primary vehicle was the Selected Acquisition Report, which required comprehensive annual submissions and quarterly updates covering baseline cost estimates, lifecycle projections, schedule and technical risk, and procurement unit cost histories. The statutory SAR requirement terminated after the final submission covering fiscal year 2023.¹¹ Section 809 of the FY 2023 National Defense Authorization Act directed the Department to replace SARs with the Modernized Selected Acquisition Report system, which now serves as the primary congressional reporting mechanism for major acquisition programs.

1
Defense Acquisition University. Acquisition Categories (ACATs)
2
Office of the Law Revision Counsel. Title 10 USC 4201 – Major Defense Acquisition Programs Definition
3
Legal Information Institute. Title 10 USC 4211 – Milestone Decision Authority
4
Office of the Law Revision Counsel. Title 10 USC 4204 – Milestone Decision Authority
5
Defense Acquisition University. Milestone C
6
Defense Acquisition University. Business System Categories (BCATs)
7
Office of the Law Revision Counsel. Title 10 USC 4272 – Independent Technical Risk Assessments
8
Office of the Law Revision Counsel. Title 10 USC Chapter 325 – Cost Growth Unit Cost Reports (Nunn-McCurdy)
9
Office of the Law Revision Counsel. Title 10 USC 4375 – Breach of Significant Cost Growth Threshold or Critical Cost Growth Threshold Required Action
10
Office of the Law Revision Counsel. Title 10 USC 4376 – Breach of Critical Cost Growth Threshold Reassessment of Program Presumption of Program Termination
11
Office of the Law Revision Counsel. Title 10 USC 4351 – Selected Acquisition Reports