Price guides are also important tools for collectors looking to sell their collection or determine their collection's worth for insurance purposes. Recently established independent companies, such as Comic Guaranty LLC (also known as CGC) and Professional Grading eXperts LLC (PGX) provide expert third party grading services for comics. Comic books can be sent to these companies for independent, impartial certification, including grading, restoration check and encapsulation within a tamper-evident protective holder.

The advent of certification enabled increased liquidity of comic books by removing disputes over grading and by disclosing restoration, and accelerated sales of comic books through online auction sites such as eBay or Heritage Auction Galleries. Certification was also a boon to comic price guide providers, as certification removes the uncertainty about the actual grade of the comic book being sold. Individual and / or aggregated reports of certified comic book sales are available online.