AIM - RAC 1.9. 4 - VFR Operations

During VFR flight in low-level airspace, adjust your transponder to reply on the
following unless otherwise assigned by an ATS unit:

(a)     Mode A, Code 1200, for operation at or below 12 500 ft ASL; or

(b)     Mode A, Code 1400, for operation above 12 500 ft ASL.

Upon leaving the confines of an airspace for which a special code assignment has been
received, the pilot is responsible for changing to the code shown in (a) or (b), unless
assigned a new code by an ATS unit.

NOTE: When climbing above 12 500 ft ASL, pilot should select Code 1200 until he/
she leaves 12 500 ft ASL, then select Code 1400. When descending from above
12 500 ft ASL, a VFR pilot should select Code 1200 upon reaching 12 500 ft
ASL. Aircraft equipped with a transponder capable of Mode C automatic
altitude reporting should adjust their transponder to reply on Mode C when
operating in Canadian airspace unless otherwise assigned by an ATS unit.