Cap-and-invest third-party emissions verification

In 2022, the Greenhouse Gas (GHG) Reporting regulation was updated to include a broader group of industries and to align with the requirements of the cap-and-invest program. It was also updated to include an additional quality-assurance mechanism: third-party emissions verification.

Emissions reports submitted to us are reviewed and verified by our staff. Under the updated rule, certain reporters must also contract with a third-party verifier. These independent verifiers will review each entity's annual emissions reports and send us a statement each year indicating whether or not the reports are accurate.

How do I know if my business needs to hire a third-party verifier?

All businesses that are subject to, or are voluntary participants in, the cap-and-invest program are required to have their emissions reports verified by a third-party verifier. However, other businesses reporting emissions under Chapter 173-441 may also be required to do so, depending on their emissions levels:

  • Threshold for reporting emissions: 10,000 metric tons
  • Threshold for third-party verification: 25,000 metric tons
  • Threshold for coverage under cap-and-invest: 25,000 metric tons after accounting for exemptions set in state law.

In addition, any reporter that drops below the 25,000 MT CO2e threshold must still have its emissions reports verified for the first year. 

Resources for reporters

How do I find a third-party verification body?

Lists of Washington-certified verification bodies are available below. 

The links above download a .zip file containing an Excel sheet. Use the (PDF) links to download an accessibile .pdf file of the lists. 

See our verifications guidelines or frequently asked questions for additional guidance on third-party verification. 

Introduction to Third-Party Verification for Reporters

In October 2023, we held a training covering how to begin the third-party verification process in the GHGReg platform, what to expect during the verification process, and how to prepare.

Request the 3PV for Reporters training

Additional third-party verification trainings for emissions reporters will be listed here, once scheduled.

For trainings on how to report emissions, see our Emissions page. Refer to the Third-Party Verification Guidelines for more detailed information and instructions on third-party verification. 

Forms for reporters and third-party verifiers are currently in development and will be available through the GHGReg website for registered reporters and verifiers.

Verification tips for reporters

Resources for verifiers

Both verification bodies and individual verifiers must meet certain requirements to be certified in Washington, including:

Individual verifiers must also complete the Washington third-party verification training. Both lead verifier and specialized sector certification require demonstration of additional work experience and corresponding certification.

All eligible verifiers and verification bodies are invited to register in Washington using our GHGReg application

Past trainings

To request a recording of a training, or to be added to an email list for announcements of upcoming trainings, please email




August 2023

Third-Party Verification Manual released

August 2023

GHGReg User Manual for Verifiers released

Sept. 13, 2023

Third-Party Individual Verifier Certification Training 

This training covers Washington’s general verification requirements.

Sept.20,  2023

Introduction to GHGReg for Verifiers Training 

This training introduces the usage of the online GHGReg platform for initiating a third-party verification process, reviewing GHG emission reports, and entering a verification statement.

Sept. 27,  2023

Third-Party Individual Verifier – Process Specialist Certification Training 

This training covers Washington’s verification requirements for process emissions.

Oct. 25,  2023

Third-Party Individual Verifier – Transaction Specialist Certification Training

This training covers Washington’s verification requirements for transaction emissions.

Nov. 8, 2023

Third-Party Individual Verifier – Oil and Gas Specialist Certification Training

This training covers Washington’s verification requirements for oil and gas emissions.

Forms for reporters and third-party verifiers are currently in development and will be available through the GHGReg website for registered reporters and verifiers.

Conflict of interest

The purpose of the third-party verification requirement is to ensure submitted emissions reports are accurate. To serve this purpose, it is important that verifiers be impartial when reviewing reporter submissions. This requires avoiding any potential conflict of interest as outlined in Chapter 173-441-085 (7)(c)  

Conflict of interest can be: 

  • Low: verification relationship will be approved 
  • Medium: verification may proceed with an approved mitigation plan
  • High: verification relationship will not be approved.