There is no one document that will cover every country I'm afraid, some common operating practices are good wherever you operate, reporting an altitude when you vacate is one of them, some ARTCC's will need something different, consider this local procedures.
Here is some information from the Airman's Information Manual in the USA, not regulatory, just a good operating practices that may need to be modified depending on what part of the world you operate in.
5-3-3. Additional Reports
a. The following reports should be made to ATC or FSS facilities without a specific ATC request:
1. At all times.
(a) When vacating any previously assigned altitude or flight level for a newly assigned altitude or flight level.
(b) When an altitude change will be made if operating on a clearance specifying VFR-on-top.
(c) When unable to climb/descend at a rate of a least 500 feet per minute.
(d) When approach has been missed. (Request clearance for specific action; i.e., to alternative airport, another approach, etc.)
(e) Change in the average true airspeed (at cruising altitude) when it varies by 5 percent or 10 knots (whichever is greater) from that filed in the flight plan.
(f) The time and altitude or flight level upon reaching a holding fix or point to which cleared.
(g) When leaving any assigned holding fix or point.
Happy aviating, D.L.
