A good monthly statement is a letter you can actually read. It is not a dump of every transaction the software happened to log. If you have to reconstruct the month from the raw lines, the statement has already failed.
Rent, plainly
You should see, in one place, what was due, what arrived, and what is still open. Not a mystery, and not a net that hides a late payment behind a prepaid one. If a resident paid on the fourth instead of the first, the page should say so in language you do not have to decode.
Ask: can I tell, in ten seconds, whether the month’s rent is in?
What went out, and why
Repairs, vendors, supplies, the management fee. Each should carry a sentence a neighbor would understand. If a cost is unusual, there should be a note before you have to ask.
Ask: if I handed this page to someone who does not know the property, would they know what was done?
Reserves and what is coming
A statement that only looks backward is half a letter. You should see the reserve, and you should see anything already scheduled — a roof being quoted, a turnover underway, a lease that ends next month.
That is the whole test. A statement you actually read, on the fifteenth, without a call.