We regularly monitor sales rates to look for authors and publishers incurring significant sales but where we do not have resale certificate(s) on hand – or if those certificates are on hand but expiring or invalid (for example due to the lack of a signature). In most cases, we would be getting in contact via our tax partner Avalara, who when getting in contact should indicate the specific reason why, as well providing a link to CertExpress to either upload fresh certificates or use the wizard to create fresh certificates as required.