After a period of rapid growth online research has entered a period where concerns about data quality have led to widespread questioning of its validity. As a consequence, clients increasingly seek assurances that the results we produce with online studies are reliable enough to use as the basis for important business decisions. This paper considers panel data quality issue from the client's perspective and suggests a limited set of issues for clients to consider as part of a fit-for-purpose test for online. These extend beyond the usual concerns about panel recruitment and management practices. They include the interplay between the research topic and Internet penetration, the potential for mode effects, and the evaluation of online results in the broader context of other sources of industry, business, and marketing information.