Question: Virginia Subscriber Answer: In the past: Prior to Jan. 1, you used type of service code "F" (ASC facility usage for surgical services) when modifier SG appears on an ASC claim. You will still use the TOS code "F" for the ASC charges for 2008. Otherwise, you should report TOS "2" (Surgery) for professional services rendered in an ASC. The TOS code 2 is for the professional claim only.