Bookworm,
In the case of Germany you are correct - For IFR flights the altitude at and below which the pilot shall set the altimeter to the QNH value transmitted by the competent ATC unit and above which he shall use the standard altimeter setting is established at 5000 ft MSL (transition altitude). For flights above the transition altitude, an altitude is established which, taking into account the valid QNH value, corresponds to the flight level for IFR, at least 1000 ft above the transition altitude (transition level).
Thus in Germany the transition level is always an IFR level. That is not the case everywhere.
Every country is different.
For example in Poland - the trasnition altitude is 6500ft AMSL and the transition Level is FL80 unless the QNH is 995 or less when it is FL90.
ENR 1.7 of the AIP for whatever country you want to fly in will let you know what the requirements are.
Regards,
DFC