How to Start a Plumbing Business in Delaware

You Need the Master License Before Anything Else

Delaware doesn't issue a standalone "plumbing contractor license." The business authority to operate a plumbing firm flows directly from holding an active Master Plumber license issued by the Board of Plumbing, Heating, Ventilation, Air Conditioning and Refrigeration Examiners through the Division of Professional Regulation.

Without a master of record, a business entity cannot pull permits, sign commercial contracts, or legally perform plumbing work. If you're still working toward your Master license, the complete licensing guide covers the application process, experience documentation, and exam logistics.

Step 1: Register Your Business Entity

Delaware's One Stop Business Registration portal at the Division of Revenue handles entity formation and tax registration in a single filing. You'll choose your business structure — sole proprietorship, LLC, or corporation — and register for a Delaware business license.

The Division of Revenue charges $75 per year for the business license. If you're forming an LLC, there's an additional $90 filing fee with the Division of Corporations, plus a $300 annual franchise tax.

You'll also register for gross receipts tax (Delaware has no sales tax, but it does tax gross receipts) and employer withholding if you plan to hire employees.

Step 2: Register as a Contractor With DPR

Separate from your individual Master Plumber license, the Division of Professional Regulation requires a contractor business registration. This $100 filing links your business entity to your personal license number and makes you the "master of record" for the firm.

This registration is what authorizes your business — not just you personally — to pull permits and accept plumbing contracts. If you later bring on additional master plumbers or journeymen, their individual licenses get linked to your firm's DPR contractor registration.

Step 3: Secure Insurance

Delaware requires plumbing contractors to carry general liability insurance of at least $100,000 per occurrence and property damage insurance of at least $300,000 per occurrence. You'll need to provide a certificate of insurance to the Division of Professional Regulation as part of your contractor registration.

Workers' compensation insurance is mandatory if you have any employees. Even if you're starting as a one-person operation, most commercial clients and general contractors will require proof of workers' comp before they'll hire you as a subcontractor.

Bonding is not required at the state level for plumbers in Delaware, though some municipalities may require it for public works projects.

Step 4: Handle Local Registration

Your state DPR registration covers your authority to practice statewide, but local jurisdictions add their own requirements:

New Castle County requires a contractor business registration with the Department of Land Use. The annual fee for non-exempt contractors is $400, plus a $10 ICC Digital Code Access fee. You'll need this registration before submitting any permit applications through the county's eServices portal.

City of Wilmington requires a separate city business license through the Department of Licenses and Inspections. Permit fees in Wilmington are calculated at $12 per $1,000 of project valuation, with a $50 Certificate of Compliance fee on top.

City of Dover and City of Newark each maintain their own local contractor licensing, zoning reviews, and permitting tracks independent of the county systems.

If most of your work will be in unincorporated Kent or Sussex County, permitting runs through the Delaware Division of Public Health, which charges a flat $100 per plumbing permit.

Step 5: Set Up Your Operations

With the licensing and registration paperwork handled, the practical side of running a plumbing business in Delaware comes down to a few operational basics:

Vehicle lettering. Most plumbing contractors display their business name and license number on service vehicles so inspectors and clients can match the truck to the permit.

Permit pulling workflow. Different jurisdictions use different portals — New Castle County's eServices, Wilmington's Finance portal, and DPH's permit system for state-controlled areas. Set up accounts on each portal where you plan to work.

Inspection scheduling. The Division of Public Health requires three business days' notice for inspection scheduling. The first three inspections per permit are included; re-inspections cost $50 each. Local jurisdictions have their own timelines.

Continuing education. Starting with the October 2026 renewal cycle, all active master plumbers must complete 5 hours of Board-approved CE every two years. Build this into your calendar now — late renewals trigger a 100% CE audit.

Common Mistakes That Delay New Plumbing Businesses

The most expensive mistake is starting the DELPROS contractor registration before gathering all required documents. The portal's 180-day application timeout applies to contractor registrations the same way it applies to individual license applications — if your filing sits incomplete for six months, the system deletes it.

The second most common mistake is assuming the state DPR registration covers local permitting authority. It doesn't. Each jurisdiction where you plan to pull permits requires its own registration, and working without proper local authorization can result in stop-work orders and fines.

The Delaware Plumber License Guide includes a business setup checklist that walks through each registration step with the specific forms, fees, and portal links you need.

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