Direct Answer
In Billings, septic system installation & replacement work generally requires a permit when the project exceeds $5,000 or involves system replacements. Your licensed contractor should pull the permit — if they ask you to pull it yourself, that's a red flag. Unpermitted work can cause problems when selling your home.
Full Explanation
Billings follows MT state building codes administered by the local building department. Permit fees vary by project value. All inspections must be scheduled through the Billings building department. Keep all permit documentation — required for home resale disclosure.
Local Factors in Billings
📍MT permit threshold: $5,000
📍Billings building department issues local permits
📍Sales tax on materials: 0% (no sales tax)
📍Permit records are public and transfer with the home