Plan number (PN)
Three-digit identifier assigned by the sponsor to each plan they sponsor.
Definition
Plan number (also called PN or plan sequence number) is a three-digit ID the sponsor assigns to each retirement plan. The first 401(k) or pension plan adopted by a sponsor is generally numbered 001; the second 002, etc. Once assigned the number must not change for the life of the plan and is reported on Form 5500-EZ line 1b.