I wouldn't think that they should bill for an office visit for EVERY visit. At least the DC's that I bill for. Most visits consist of a manipulation and modalities, but not an E&M office visit. Of course the first visit since they are gathering information, patient history, family history, etc. They are also allowed to bill for reevaluations. WC & NF allow reevals approx 6-8 weeks after initial eval, or last reeval. Insurance carriers rules vary on whether they allow reevals so you need to check with each carrier.
Michele