Although the FDA does not require expiration dates on supplements, Thrivous supplements include a "best used by" date, which is printed on the bottom of the bottle during the manufacturing process. The "best used by" date is usually two years from the time of manufacturing.
Individual ingredients in supplements may have an expiration or retest date set by the supplier, as disclosed in the certificate of analysis that Thrivous publishes. These dates indicate the recommended date by which the material should be tested again to ensure quality. They do NOT mean that the material is no longer safe or effective after the date.
FDA has performed extensive stability testing of numerous pharmaceutical products. In 2006, the Journal of Pharmaceutical Sciences published an analysis of the FDA's stability test data. The analysis found that 88% of products maintained stability at least 1 year beyond their original expiration date for an average extension of over 5 years. And the analysis concluded that "the stability and quality of extended drug products can only be assured by periodic testing and systematic evaluation".
Accordingly, at time of manufacturing, Thrivous and third-party labs re-test all supplement ingredients and their combination to ensure quality. Tests generally include at least identity, potency, microbial, and heavy metals. Finished products are only shipped if they pass all tests.