What was my actual investment return last month?

Reconcile last month's investment result using opening and closing value, deposits, withdrawals, dividends, fees, realized gains, and unrealized gains without mistaking new money for performance.

Start with the question you actually want answered

“How much did I make?” can mean three different things: the dollar gain in the account, the return generated by the investments, or the return experienced by you after the timing of deposits and withdrawals. Those figures can all be correct and still disagree.

For a monthly review, show at least two answers side by side: cash-flow-adjusted profit in money and a percentage return. Keep the method label visible so a broker balance change is not mistaken for investment skill.

Reconcile the month in dollars before calculating a rate

A practical profit check is: closing portfolio value minus opening portfolio value, minus external deposits, plus external withdrawals. If the portfolio began at $40,000, ended at $46,500, and received a $5,000 deposit, the cash-flow-adjusted gain is $1,500, not $6,500.

The opening and closing values should include invested assets and portfolio cash. Transfers between your own brokerage accounts are internal movements when both accounts are included; counting one side as a deposit can create a false gain or loss.

Treat dividends, interest, fees, and tax consistently

Dividends and interest are investment income, whether paid to cash or automatically reinvested. They belong in total return. External deposits and withdrawals are not performance and must be separated from income rows.

Use net performance when reviewing what you actually kept: include trading fees, management fees, withholding tax, and other portfolio costs consistently. CFA Institute's GIPS overview requires transaction costs in return calculations and cash equivalents in total return, which is a useful discipline even for a personal ledger.

Do not add realized and unrealized gains blindly

Realized gain explains what was crystallized by sales; unrealized gain explains the change still embedded in open positions. They are useful attribution views, but the monthly account-profit reconciliation remains the control total.

A sale moves value from a security into cash. It does not create a second gain on top of the portfolio value change. Add realized and unrealized components only when both are calculated over the same period, from consistent cost-basis and valuation data, with income and costs handled once.

Choose time-weighted or money-weighted return for the job

Time-weighted return breaks the month at external cash flows and links the sub-period returns. It is the better measure for comparing the portfolio's investment performance with a fund or benchmark because the timing of your deposits is removed.

Money-weighted return, usually calculated as IRR or XIRR from dated cash flows, reflects the size and timing of your own contributions and withdrawals. Vanguard calls this a personal rate of return; it can differ materially from an index because it measures your capital experience rather than a manager-only result.

Worked example: one month, three valid numbers

Suppose an account opens at $20,000, receives $8,000 near month-end, pays a $120 dividend, incurs $20 of fees, and closes at $29,000. The cash-flow-adjusted monthly profit is $1,000. The $8,000 deposit increased wealth but did not create investment profit.

A simple $1,000 divided by $20,000 gives 5%, but that shortcut ignores when the deposit arrived. A proper time-weighted return values the account immediately before the cash flow; a money-weighted return uses the actual dates. If daily valuations are unavailable, label any approximation instead of presenting it as exact.

Explain why the broker screen may show another result

Broker screens may use different cut-off times, settlement dates, FX rates, fee treatment, tax treatment, or definitions of “return.” One view may cover one account while another consolidates several accounts and cash balances.

Reconcile the inputs before judging the formula: month-end positions, cash, deposits, withdrawals, dividends, fees, and prices. A durable ledger should preserve the source transaction and the valuation date so the difference can be explained rather than overwritten.

What Portle should calculate every month

The monthly result should show opening value, closing value, net external cash flow, cash-flow-adjusted profit, dividends, fees and taxes, realized and unrealized attribution, time-weighted return where valuations allow it, and personal money-weighted return where dated cash flows allow it. Periods shorter than one year should not be annualized.

Benchmarks: Vanguard's personal-rate-of-return explanation (personal.vanguard.com/us/content/MyPortfolio/performance/LMperfSummaryInfoContent.jsp), Morningstar's Total Return vs. Personal Return guide (portfolio.morningstar.com/Rtport/Reg/TotalvsPrsnalRtrn_Learn.html), and the CFA Institute GIPS overview (cfainstitute.org/insights/professional-learning/refresher-readings/2026/overview-of-the-global-investment-performance-standards). Connect a complete Google Sheets ledger to Portle so the same reconciliation runs each month without rebuilding it.