All wines for sale in the United States that contain 10 or more parts per million (ppm) sulfur dioxide must bear a label stating "Contains Sulfites" (27 CFR 4.32(e)). This labeling requirement allows those people who may have an allergic reaction to sulfur dioxide to be aware of its presence in wines.
The Food and Drug Administration has determined that products that contain less than 10 ppm of sulfites (such as sulfur dioxide) do not have to include this declaration on the label or they can label the product with the statement "contains less than 10 ppm sulfites." These wines require a sulfur dioxide waiver for such labeling.
For sulfite waivers, the winemaker must have proof of sample analysis from a TTB-certified laboratory or from TTB (Compliance Laboratory). You must submit that evidence, in the form of an official laboratory report, with the application for label approval.