The single most common error I see in federal retirement planning is not a math error. It is an assumptionerror — someone believing they are under FERS (or CSRS, or CSRS Offset) when in fact they are under a different system. The error is rarely caught before the annuity estimate arrives, and by then the levers that would have fixed it are mostly gone.

So before you plan, you verify. Here is how, in under five minutes, three different ways.

Method 1: The SF-50 (the fastest).

Your most recent SF-50 Notification of Personnel Action contains a box labeled “Retirement Plan.” The two-digit code in that box is the answer:

  • Code 1— FERS (most federal employees hired on or after January 1, 1987).
  • Code 2— CSRS (most federal employees hired before January 1, 1987 with continuous service).
  • Code 3— CSRS Offset (hybrid coverage).
  • Code 6— FERS-RAE (Revised Annuity Employees, hired in 2013 or later).
  • Code K— FERS-FRAE (Further Revised Annuity Employees, hired in 2022 or later, with a slightly higher employee contribution).

Pull your SF-50 from eOPF (the Electronic Official Personnel Folder). It takes two minutes if you know your login, longer if you don’t.

Method 2: The SF-3107 Individual Retirement Record.

The SF-3107(and its modern electronic equivalent) is the document that shows every period of creditable service, the system applied to each period, your total years of service, and any redeposits or service credit purchases you’ve made.

This is the document to look at when your history is non-trivial — prior military service, breaks in federal employment, periods of leave without pay, refunds that may or may not have been repaid. The SF-50 tells you the current code. The SF-3107 tells you the story.

Method 3: Ask your HR specialist (the slowest, sometimes most useful).

For most employees, the agency HR specialist can confirm your retirement system in a single email. There are two caveats.

First, HR specialists are generalists. They will usually know your current code but may not know what to do with it. Don’t ask them “what should I do about it?” Ask them “what is my retirement plan code on my most recent SF-50?”That’s a question they can answer cleanly.

Second, if you have any prior federal service — civilian, military, or contractor-adjacent that was actually federal — make sure the HR specialist is looking at all of it, not just the most recent SF-50. The current code may not reflect your full history, and the gaps are where mistakes get made.

Why this matters before you plan.

The retirement system code determines the multiplier, the survivor election rules, the Social Security interaction, the TSP match, and the eligibility thresholds for every kind of retirement (immediate, deferred, disability, VERA, phased). It is also essentially locked in — you don’t choose your retirement system. It was determined by your hiring date, your position, and the rules in effect when you were hired.

The cleanest way to start any federal retirement plan is with that code, confirmed in writing, before any other number is touched. Everything downstream depends on it being right.