Four questions expose most of what matters. Is the return net of all fees or gross? Is it time-weighted-return or money-weighted-return? What benchmark, on what return basis? And does the record include every account run in the strategy, or a selection?
Common distortions include start dates chosen at a trough, simulated results presented alongside live ones without clear labelling, composites that quietly drop closed accounts, and annualised figures computed from periods shorter than a year.
Good reporting shows the full history, states the methodology, publishes risk figures such as max-drawdown alongside return, and separates live from backtested. Anything less is marketing. See gips-standards and backtesting.
Related: gips-standards, time-weighted-return, money-weighted-return, max-drawdown, backtesting, benchmark