If patient has 2 insurances, you bill the first insurance - now sending to 2nd insurance company (with attached EOB of course) but they don't have this CPT code listed as a billable service - but there is a different code they use - Question: If we locate both billing codes on the note - can you legally change the billing code to bill the second insurance? If the 1st insurance doesn't pay anything and now trying 2nd insurance, is it legal only at this time to change the billing code? OR is it always illegal to change it. Some providers use HCPC codes for services or their own billing code while there is an equivalent is a CPT code at another insurance. Not sure what the legalities are with this. Some staff think that only one code can be used and you can never change it once it is billed at all. Thanks.