Vendor Information

We appreciate our vendors and as a result we've developed this website to make it easier for our vendors to help us. Please review the brief description of necessary information below. If you have feedback you can provide it to us at or through our online comment form.

The Department of Public Works issues invoices for a variety of services and processes payment to vendors for sales of services and products for the following County departments and Special Districts:

  • County Roads
  • Water-Sewer Utilities
  • Solid Waste Utilities
  • Stormwater
  • Fleet Operations; including ER&R and Motor Pool
  • Three Rivers Regional Wastewater Association
  • Silver Lake Flood Control District
  • Lexington Flood Control Zone District
  • Consolidated Diking Improvement District #2
  • Consolidated Diking Improvement District #3
  • Diking Improvement District #15
  • Drainage Improvement District #1

Washington State Department of Revenue is the regulatory agency for sales tax. Vendor invoices for sales of services and products should include sales tax as applicable. Deliveries that occur within the city limits of Longview and Kelso are currently taxable at 8.0% under tax code 0800. The tax code for the rest of Cowlitz County is 0803 which is currently 7.9%. Delivery, freight, and setup costs are typically taxable. Invoices that are issued by the Department of Public Works for permits and other governmental services may include sales tax if applicable.

New vendors will need to submit an IRS form W-9 to certify their business information prior to payment being issued by Cowlitz County.

Vendors may submit invoices for payment in person or by mail at the Public Works address, or electronically by fax @ (360)636-0845 or by email to Invoices for purchases by Fleet Operations division should instead be submitted by email to

Invoices are paid by the County Auditor and mailed, typically within 45 days of receipt of invoice or goods. Whichever is latter. Vendors are paid by County Warrant which is mailed each Friday. Vendors may request to pick up their warrant at the Auditor's office by calling (360) 577-3002. Their office is located on the second floor of the County Administration Building at 207 Fourth Avenue North in Kelso. Identification will be required.

Approval of invoices is contingent on completion of work included on the invoice, delivery of satisfactory product, and submission and/or filing of other documents required by contract or statute. This may include documentation and verification of expenses requested for reimbursement, certified payroll and prevailing wage documents, as well as other documents and filings which may be required. Failure to deliver satisfactory product, file necessary documents with regulatory agencies and to supply other required documentation may result in delayed payment. Retainage may be applicable and may be withheld on public works contracts. To inquire on payment status or if you have questions on documentation and filing requirements, please call our office at (360) 577-3030.