tomek_m22:
Don't quite follow your question as most Part 135 ops define the when/where of these checks, at least on this side of the pond. Also while different OEMs can use different terminologies a power trend check is different than a power assurance check.
Without knowing your specific aircraft/engine here are some general points.
The ops I familiar with, EMS and Oil & Gas, use a daily power trend check depending on aircraft type. This is usually taken in cruise at a defined altitude and torque setting. The pilot would record OAT, TOT, and other data as required. It varied between aircraft models but served the same purpose.
In most cases a power assurance check is only used if the trend checks show a problem, a scheduled inspection as you mentioned, a post-maintenance requirement, or other similar event.
I don't recall any aircraft that required a daily assurance check unless it was operator specified. I've seen some external load guys do one pending conditions to see how the aircraft performed prior to flying a load in confined areas.
So it all depends on the circumstances.