250 blw 10,000 in the U.S.

The FARs go on to say that unless needed for operation reasons.

Most widebodies below require above 250 blw 10K to clean up. My intrepretation of the FARs (No, I'm not an expert, nor even close) is that you should give a courtesy call to either clearance delivery and/or departure control that you will be exceeding 250/blw10K for operational reasons but it is not required. Most ATC controllers can put 2 and 2 together if you are in a widebody aircraft departing heavy on a long flight.