Illinois vs Missouri Electrical Code
Side-by-side comparison
| Factor | Illinois | Missouri |
|---|---|---|
| NEC edition | NEC 2008 | Local jurisdictions |
| Compliance score | 47/100 (Permissive) | 20/100 (Minimal) |
| Electrician license | Required | Not required statewide |
| License name | Electrical License (varies by jurisdiction) | No statewide license (local may apply) |
| Permits required | Yes | Yes |
| State amendments | No | No |
| Homeowner exempt | Yes | Yes |
Key differences
- Missouri uses a more recent NEC edition (local_only vs 2008), meaning it has the latest safety requirements including expanded GFCI coverage and updated load calculation methods.
- Illinois requires a statewide electrician license while Missouri does not, meaning licensing in Missouri is handled at the city/county level.
Licensing requirements
Illinois
Illinois requires a Electrical License (varies by jurisdiction) through the Local jurisdictions (no statewide license). Homeowners are exempt for work on their own primary residence.
Missouri
Missouri does not require a statewide electrician license. Requirements are set by local jurisdictions.
Wire sizing is identical. NEC Table 310.16 ampacity values have not changed since NEC 2017. Whether you are wiring in Illinois or Missouri, a 20A circuit uses 12 AWG copper and a 30A circuit uses 10 AWG copper. The differences between states are in code enforcement, not in the wire sizing itself.
GFCI requirement differences
Because Missouri uses NEC local_only and Illinois uses NEC 2008, there are differences in GFCI coverage:
The GFCI differences between NEC local_only and NEC 2008 are minor for most residential work. The most significant changes came in NEC 2023 with expanded kitchen and basement coverage. See our GFCI guides by room for details.
Frequently asked questions
Which state has stricter electrical codes, Illinois or Missouri?
Illinois has stricter enforcement with a score of 47/100 vs 20/100. The score reflects NEC edition recency, licensing requirements, permit enforcement, and state amendments.
Is my electrician license from Illinois valid in Missouri?
Electrician licenses are generally not transferable between states. If you hold a license in Illinois, you will typically need to apply separately in Missouri. Some states offer reciprocity agreements, but these vary. Contact the licensing authority in Missouri directly for requirements.
Is the wire size different in Illinois vs Missouri?
No. Wire sizing per NEC Table 310.16 is identical regardless of which NEC edition a state enforces. A 20A circuit requires 12 AWG copper in both Illinois and Missouri. The ampacity values have not changed since NEC 2017.
Do both Illinois and Missouri require electrical permits?
Both states require electrical permits for most work. Common permit-required projects in both states include new circuits, panel upgrades, service changes, and EV charger installations.
Does the NEC edition difference between Illinois and Missouri matter for my project?
For most residential work (circuits, outlets, fixtures), the NEC edition difference has minimal practical impact because wire sizing tables are unchanged. The biggest difference is GFCI coverage: NEC 2023 requires GFCI in all kitchen outlets and finished basements, while older editions are narrower. If you are doing a kitchen or basement remodel, the edition difference matters.
NEC 2023 references verified April 2026