An account begins a period at 1,000 and ends at 1,300. Calling the change a 30% investment return would ignore any money added during the period.
Reconcile the amounts first
In a deliberately simplified example, suppose you contributed 250, made no withdrawals and have no other separately recorded cash flows. The remaining change is 50: 1,300 − 1,000 − 250.
That amount is not automatically a 5% return. Calculating a meaningful rate requires attention to when the contribution occurred and what the chosen method includes. Fees, distributions and other account events may need separate treatment.
Read the statement labels
Distinguish balance change, contributions, income and reported performance. If a statement supplies a return figure, look for its methodology rather than reconstructing it from the opening and closing balances alone.
Keep transfers visible too. Money moving between accounts can look like growth in one place and decline in another without representing an investment gain or loss.
Turn uncertainty into a question
Write down the transaction dates and the specific label you do not understand. Ask the provider for an explanation of the calculation rather than assuming an error.
Use an assumptions check when reading a book’s simplified illustration. A rising balance can be encouraging while still requiring a careful explanation of where the increase came from.