The Systems Engineering Plan (SEP) is a living document that details the execution, management, and control of the technical aspects of an acquisition program from conception to disposal. The SEP outlines how the systems engineering process is applied and tailored to meet objectives for each acquisition phase. The SEP captures a program’s current and evolving systems engineering strategy and its relationship with the overall program management effort. The SEP should include the process and criteria for updating the document.
Definition: A Systems Engineering Plan (SEP) is a “living” document that captures a program’s current and evolving systems engineering strategy and its relationship with the overall program management effort. The SEP purpose is to guide all technical aspects of the program. 
Systems Engineering Plan (SEP) Purpose
The purpose of the SEP is to help program technical managers develop their systems engineering approach—providing a firm and well-documented technical foundation for the program. A rigorous technical planning process forces thoughtful consideration and debate, allows for integration and coordination of technical activities across all levels of management, and results in a sound systems engineering strategy commensurate with the program’s technical issues, life cycle phasing, and overall objectives.
Systems Engineering Plan (SEP) Development
The Program Manager is responsible for the development of the SEP. The SEP should be developed with the Chief Systems Engineer and other subject matter experts. The document is considered a “Living Document” and is updated continually throughout the program. The basic approach to developing a SEP is listed below.
- Step 1: Break the SEP into functional areas (utilize the template to ensure each functional area is addressed)
- Step 2: Assign a lead to develop each functional area
- Step 3: The SEP lead should use formal or informal working groups to address specific planning issues
- Step 4: Establish a specific plan of action and schedule/milestones (POA&M) to complete
- Step 5: Develop actual SEP by inputting each function lead and are.
- Step 6: Submit SE for the review cycle
- Step 7: Finalize the SEP with the team.
An outline/template is always a great place to start when developing a SEP. The template will make sure you address all the key areas that need to be addressed in the SEP and give you a great idea of what information is needed. Below is a great template/outline you can use in developing your SEP.
Systems Engineering Plan (SEP) Approval
REGULATORY: A draft update is due for the Development RFP Release Decision Point and approved at Milestone B. The Deputy Assistant Secretary of Defense (Systems Engineering) (DASD(SE)) is the approval authority for Major Defense Acquisition Programs (MDAP) and Major Automated Information System (MAIS) programs; the Component head or as delegated will approve the SEP for all other programs. 
Systems Engineering Plan (SEP) Updates
The SEP is updated as needed to reflect technical progress and changes in the technical approaches stemming from the findings and results of the technical reviews, program reviews, acquisition milestones, or other program decision points. The SEP is updated and submitted for Milestone Decision Authority (MDA) approval at each program milestone. A draft update is due for the Development RFP Release Decision Point and approved at Milestone B.
Systems Engineering Plan (SEP) Focus Areas
The Office of the Secretary of Defense (OSD) suggests that programs organize the SEP according to five critical focus areas: 
- Program Technical Requirements: The SEP should define how the program will manage all requirements (statutory, regulatory, derived, and certification).
- Technical Staffing and Organization Planning: The SEP should show how the program will structure and organize the program team to satisfy requirements.
- Technical Baseline Management: The SEP should establish a technical baselines approach.
- Technical Review Planning: The SEP should show how the program will manage the technical effort, including the technical baselines, through event-based technical reviews.
- Integration with Overall Management of the Program: The SEP should link SE to other management efforts, including the Acquisition Strategy, test planning, sustainment planning, Configuration Management, Risk Management, and life-cycle management.
Systems Engineering Plan (SEP) Software Planning
The program SEP provides an opportunity to integrate software planning into a program’s overall systems engineering planning. This is critical to ensure proper allocation of resources, schedule development, and overall software understanding.
Systems Engineering Plan (SEP) Referenced Documents
Key documents that refer to the Systems Engineering Plan and should be coordinated with:
- Initial Capabilities Document (ICD),
- Capability Development Document (CDD)
- Concept of Operations (CONOPS)
- Acquisition Strategy
- Risk Management Plan (RMP)
- Configuration Management Plan
- Integrated Master Plan (IMP)
- Integrated Master Schedule (IMS)
- Test and Evaluation Master Plan (TEMP)
- The Systems Engineering Plan (SEP) is not a Systems Engineering Management Plan (SEMP). The SEMP is developed to manage the development of a system by a contractor. It’s written in response to a government SEP and provides a unique insight into applying a contractor’s standards, capability models, and toolsets to the development of a system.
- The SEP should be established early in the program definition stages and updated periodically as the program matures. Programs can manage cost, schedule, and performance by starting systems engineering processes early and monitoring them through the life cycle.
- Software planning in the Systems Engineering Plan
AcqLinks and References:
-  DoD Systems Engineering Preparation Guide – April 2008
- System Engineering Plan (SEP) Outline Version 3.0 – 12 May 2017
- (Old) Systems Engineering Plan Outline – 20 April 2011
- (Old) DoD Systems Engineering Preparation Guide – April 2008 (Superseded by SE Plan Outline)
- SE Plan Frequent Questions
- How to Prepare a SEP that Works
-  Website: DAU Acquipedia “Systems Engineering Plan”