It’s fine to use acronyms when you’re absolutely sure the reader will understand you. But when in doubt, spell it out.
The general rule is to spell out an acronym in its first use, and follow it with the acronym in parentheses. You can then use the acronym by itself in later sentences.
I’ll give you my opinion as soon as I get the Pre-Sentence Investigation (PSI) report. The PSI will list all prior criminal history, and I need to know that before I make my recommendations.