Ah, this is a topic that's a little bit controversial. Not sure why your software tells you it isn't allowed. A new patient visit can be billed on the same day as the Mohs procedure with a modifier 25, but the tricky part is whether or not that modifier 25 is supported - based just on what you've said, the modifier 25 may not be well supported. Medicare's guideline on this states that 'When the decision to perform the minor procedure is typically done immediately before the service, it is considered a routine pre-operative service and a visit or consultation is not billed in addition to the procedure'. So if your patient is scheduled for the procedure and the provider's evaluation and management is entirely related to what is required to do that procedure, then it's considered normal pre-operative work and part of the global package and it's not separately identifiable E&M. However, if there is something separately identifiable that's documented, such as an additional complaint or comorbidity that has to be investigated, or testing that needs to be done, you could potentially support billing the new patient visit in addition to the procedure. My suggestion would be to review some of your documentation and make a decision as to how and whether you could make an argument to defend that visit charge if you were audited and go from there.