Question: For accounting purposes, we need to bill the professional and technical components of our sleep lab services separately. We-re billing two line items with identical procedure codes, but append modifier TC or 26. Why are we being denied for duplicate services? Maryland Subscriber Answer: If you-re reporting the service with both modifiers TC (Technical component) and 26 (Professional component) on the same day with the same tax identification number, you should be billing globally instead, which means one line item with no modifiers. You must develop another -work around- for your accounting system or face denials. If your physician reads the results several days after the sleep study, you should be able to bill each service with the appropriate modifier because of the different dates.