Winery Due Diligence Checklist: Permits, Licenses, Water, Wastewater
Winery due diligence asks whether the property and business can legally keep doing what they do today, at the volume and visitation you are paying for. That means comparing the county use permit with actual operations, confirming how federal and state licenses will move to you, and checking water supply, process wastewater coverage, buildings and fire access, environmental conditions, equipment and contracts. A winery can have sound buildings and still carry a permit, wastewater or licensing problem that changes its value.
This checklist is organized in the order we usually work through a winery purchase in Napa and Sonoma. It complements our vineyard due diligence guide, which covers vines, soils and farming, and our longer guide to buying a vineyard or winery property.
How to use this checklist
- Start before the letter of intent. Ask for the use permit and conditions of approval early, because they shape the price and the deal structure.
- Set a realistic contingency period. County records requests, wastewater review and license planning take longer than a house inspection.
- Assign each item. Your broker gathers documents, an alcohol beverage attorney handles licensing, a land-use consultant reads the permit, and engineers cover water, wastewater and buildings.
- Decide the structure first. Buying the assets and buying the company lead to different filings; see our comparison of buying a winery business versus the real estate.
Diamond may refer you to partners we work with, such as attorneys, engineers and inspectors; you’re free to choose any provider.
1. Use permit and compliance history
The use permit sets what the property may be used for: production gallons, visitors, marketing events, hours and building area. The licenses let a business make and sell wine. Both have to line up.
- Get the original permit or certificate of exemption, every modification, and the conditions of approval for each.
- List the permitted limits: annual production, daily and weekly visitors, number and size of events, hours, food service.
- Compare those limits with actual production reports, visitor logs, event calendars and wine club event records for the last few years.
- Ask the county for audit results, notices of violation, code enforcement files and open applications.
- Check the 75% Napa grape rule and the 40% accessory space limit where they apply.
In Napa, compliance history carries extra weight. The 2015 Grand Jury reported that the county audited about 20 wineries a year. Press reports say the Board of Supervisors voted on March 10, 2026 to end the voluntary code compliance program, which let wineries fix permit violations while operating, as of April 30, 2026.
Vinetur quoted the planning director as saying an out-of-compliance winery must return to compliant operations for a full year before the county will consider a permit modification. The Napa Valley Register described a one-year wait as Planning Commission practice in some cases. Confirm the current policy with Napa County PBES before you pay for planned expansion.
Our guides to the Napa County winery use permit, the Winery Definition Ordinance and Sonoma County winery use permits explain how to read the documents.
2. Federal and state licenses
Licenses don’t come with the deed. Plan the filings during escrow, not after.
- TTB basic permit. TTB treats a sale of the business as a change in proprietorship and a sale of stock or LLC interests as a change in control. A successor may keep operating if it files a new basic permit application within 30 days of the change.
- Registration and bond. TTB says the successor must qualify, including registration and bond, before it begins or continues business. If approvals aren’t in place, regulated operations must stop until TTB approves in writing.
- Change in control. An amended winery application is due within 30 days, and a new member or stockholder with more than 10% who isn’t on record files a Personnel Questionnaire (TTB Form 5000.9).
- ABC Type 02 winegrower license. ABC issues a separate license to each legal entity making wine under its own bonded winery. The licensee needs facilities and equipment to convert fruit into wine and must actually produce wine.
- Add-on permits. List any ABC permits tied to the operation, such as a Type 93 estate tasting event permit or Type 81 wine sales event permit, and confirm they can be replaced.
- Server training. ABC lists the Type 02 as subject to Responsible Beverage Service requirements, so check that tasting room staff and managers are certified.
Our winery license transfer guide sets out the ABC escrow and notice steps and a closing timeline. If other brands make wine on site, read about custom crush and alternating proprietorships before you count the capacity as yours.
3. Water supply
- Collect well completion reports, permits, pump tests, meter data and water quality results.
- Find any Water Availability Analysis and the water conditions in the use permit, including monitoring and reporting.
- Confirm whether the system serves enough people to need its own water system review; the Napa winery packet asks for a water system feasibility report when 25 or more people are served.
- Check groundwater fees on the tax bill and any surface water rights for ponds or diversions.
See Napa groundwater rules for the screening limits and fees.
4. Process wastewater
Winery process water, the water used to clean tanks, barrels and equipment, has its own permit system. The State Water Resources Control Board adopted the statewide General Waste Discharge Requirements for Winery Process Water, Order WQ 2021-0002-DWQ, on January 20, 2021.
- Who it covers. According to the San Francisco Bay Regional Water Board, the order applies to facilities producing wine or grape juice that generate 10,000 to 15,000,000 gallons of process water a year discharged to land, including ponds, irrigation and septic-subsurface systems.
- Deadlines. Existing wineries without other coverage had to enroll by January 20, 2024. New and expanding wineries apply through an electronic Notice of Intent at least 180 days before starting the new or expanded operation.
- Napa’s transition. Wineries in Napa County’s Winery Waste Discharge Program that received extended coverage have until January 20, 2027 to move to the statewide order. Until then, Napa County PBES oversees existing permitted wineries under an updated memorandum of understanding with the Regional Board.
- Tiers and fees. Requirements and the annual fee depend on the tier, which is set by the volume discharged to land.
Ask for the enrollment or county permit, the technical report, monitoring reports and any notices. Check whether the system’s design flow covers the production you plan. Our guide to winery wastewater explains the systems.
5. Buildings, caves, fire and access
- Match every building, cave, crush pad and tasting space to a building permit with a final inspection.
- Confirm the occupancy approved for visitor areas and any commercial kitchen.
- Have caves inspected by an engineer familiar with them, and check ventilation and emergency exits.
- Check fire access roads, water storage for firefighting and defensible space against county and fire district conditions.
- Review accessibility for visitor areas, parking and restrooms; tasting rooms are open to the public.
- Order roof, structural, electrical, refrigeration and process piping inspections.
6. Environmental and site conditions
- Consider a Phase I environmental site assessment. EPA’s All Appropriate Inquiries rule requires the inquiry within one year before acquisition, with key parts updated within 180 days, to support federal landowner liability protections.
- Look for fuel tanks, chemical storage, old dumps and any hazardous materials business plan on file.
- Review biological, cultural and stormwater conditions in the permit, and any Williamson Act contract or conservation easement on the land.
- Check the fire hazard zone and flood zone, and price insurance early.
7. Equipment, inventory and contracts
- Equipment schedule. Tanks by size and type, barrels by age, presses, pumps, refrigeration, bottling equipment, forklifts and lab gear, noting what is owned, leased or financed.
- Inventory. Count bulk and cased wine at closing and agree who bears excise tax and compliance duties for wine removed before and after the change.
- Brand assets. Trademarks, label artwork and approvals, domain names, wine club and customer lists.
- Fruit contracts. Assignability, term, price and quality terms; see grape purchase agreements.
- Other contracts. Custom crush clients, distributors, leases, employees and service providers.
Checklist summary
| Area | Key documents | Usually reviewed by |
|---|---|---|
| Use permit | Permit, modifications, conditions, audits, violations | Land-use consultant or attorney |
| Licenses | TTB permit, registration, bond; ABC license and permits | Alcohol beverage attorney |
| Water | Well records, WAA, water system permits, fees | Hydrogeologist or engineer |
| Wastewater | Winery Order enrollment or county permit, technical and monitoring reports | Civil engineer |
| Buildings and fire | Permits and finals, occupancy, cave reports, fire conditions | Inspectors and engineers |
| Environmental | Phase I, tanks, chemicals, stormwater | Environmental consultant |
| Business assets | Equipment list, inventory count, brand, contracts | Buyer, accountant and attorney |
Our winery valuation guide explains how these findings feed into price. For a plain-language overview of the whole purchase, see our guide to buying a vineyard or winery.
This is general information, not legal or tax advice; talk to an alcohol beverage attorney, a land-use attorney or a tax adviser about a specific winery.
Questions people ask
What is the most important document in winery due diligence?
Usually the county use permit and its conditions of approval, because they set the production, visitation and events the business can lawfully run. Compare them with actual operations.
Does the winery license transfer with the property?
No. TTB requires the new owner to file for its own basic permit within 30 days of the change, and California’s Type 02 license transfers only with ABC approval.
Does a winery need a wastewater permit?
If it discharges process water to land, often yes. The statewide Winery Order covers facilities generating 10,000 to 15,000,000 gallons a year discharged to land, and Napa wineries in the county program have until January 20, 2027 to transition.
How do I check a Napa winery’s compliance history?
Ask the seller and the county for audit results, notices of violation and code enforcement files, and compare permitted limits with production and visitor records.
What happens if the winery is out of compliance with its permit?
The county can take enforcement action. Since the voluntary compliance program ended on April 30, 2026, press reports describe up to a year of compliant operation before Napa County will consider a permit modification; confirm the current policy with county planning staff.
Do I need a Phase I environmental assessment for a winery?
It’s not always required, but a lender may ask for one. Completing it under EPA’s All Appropriate Inquiries rule supports federal landowner liability protections.
How long should the due diligence period be?
Long enough to receive county records, review wastewater coverage and plan the licensing. That is usually longer than for a vineyard without a winery.
Buying a permitted winery in Napa or Sonoma? Our vineyard and winery team can build the document request list with you and coordinate the property review with your attorney and engineers.
Sources & notes
- TTB: Change in proprietorship or control, wine (updated January 9, 2026)
- California ABC: License types (Type 02 winegrower and related permits)
- San Francisco Bay Regional Water Board: Winery program
- State Water Resources Control Board: Winery Order fact sheet (updated January 3, 2024)
- Napa County PBES: Use Permit / Administrative Permit Application, Winery Uses (March 2026)
- Napa County Grand Jury 2014-2015: Are Napa County wineries following the rules? (May 12, 2015)
- Napa Valley Register: County sunsets winery amnesty program (2026)
- Vinetur: Napa County board votes to end winery code compliance program (March 12, 2026)
- U.S. EPA: Brownfields All Appropriate Inquiries
- Building, cave, fire and equipment items are general due diligence practice, not legal requirements. Confirm wastewater coverage with the Regional Water Board that covers the parcel.
Last reviewed October 2026 by Matthew Martinez.
