I would like to know what other offices do billing 99406. We have billed 99406 w/dx's to pay to 1 insurance company, and have had no trouble getting paid. This week I had 2 claims deny, for no modifier 33. I have never used this modifier on any of their claims but now they are asking for it, I do not agree. I think it is a system issue but am not sure. Does anyone have a thought Thank you Nancy