Why the Return Your Broker Shows You Is Probably Wrong

The Number You Trust Most Might Be the Least Reliable

You log into your broker, glance at the performance figure, and feel either relieved or disappointed. That number feels authoritative — it comes from the institution holding your money, after all.

But portfolio return calculation is not a standardised science at the retail level. Different brokers use different methods, apply different time windows, and handle cash flows in ways that can quietly flatter or distort your actual results. Understanding why the figure can be wrong — and what a more honest calculation looks like — is one of the most practical things you can do as a self-directed investor.

Two Fundamentally Different Ways to Measure Return

Before you can spot a misleading number, you need to know what the alternatives are.

Simple Return (What Most Brokers Show)

The most common figure is a straightforward percentage gain or loss based on current value versus cost:

This works reasonably well if you invested a single lump sum at the start and never touched the account. In practice, almost nobody does that.

Time-Weighted Return (TWR)

TWR breaks your investment history into sub-periods separated by each cash flow, calculates the return in each sub-period, and chains them together. It is the standard used by professional fund managers precisely because it removes the distortion caused by the timing and size of deposits or withdrawals. It tells you how well the portfolio strategy performed, independent of when you added money.

Money-Weighted Return / IRR

The Internal Rate of Return (IRR) is the discount rate that makes the net present value of all your cash flows — every deposit, every withdrawal, and the final value — equal to zero. Unlike TWR, IRR does account for the timing of your cash flows. It tells you the actual annualised return on your specific money, given exactly when you put it in and took it out.

Where Broker Calculations Commonly Go Wrong

1. They Ignore Uninvested Cash

If you deposited €10,000 and left €3,000 sitting in cash while the other €7,000 was invested, some platforms calculate your return only on the invested portion. Your real return on the full €10,000 is lower — but the dashboard may not reflect that.

2. They Use the Wrong Start Date

Many brokers reset their performance clock to the start of the calendar year, or to the date you opened the account, not the date you actually made each purchase. If you bought a position in March and the broker's "return" starts in January, you are seeing a figure that includes time when you did not even own the asset.

3. They Handle Dividends Inconsistently

Some platforms add dividend income to your cash balance but exclude it from the performance calculation. Others include it. If you hold dividend-paying stocks or distributing ETFs, this discrepancy can meaningfully change the reported figure.

4. They Cannot Handle Multi-Broker Reality

If you own a stock position in two different brokers, neither one knows about the other. The return each shows is partial by definition. Your actual portfolio return calculation requires consolidating everything — and that is something a single brokerage dashboard structurally cannot do.

A Concrete Example: Same Portfolio, Very Different Numbers

Imagine you invested in a European equity ETF over two years:

Simple return (broker method, cost basis): (21,500 − 17,000) ÷ 17,000 = 26.5% — but this is not annualised and ignores when each euro was deployed.

IRR (money-weighted, annualised): Running the actual cash flow dates through an IRR calculation produces approximately 9.8% per year in this example — a very different and far more meaningful figure for understanding what your money actually earned over time.

The broker's 26.5% is not technically wrong, but it is not actionable either. The IRR is what you can compare to a savings rate, a benchmark, or your own financial goals.

What to Watch Out For: When Even IRR Has Limits

IRR is powerful, but it is not perfect for every situation.

• Very short holding periods can produce extreme IRR figures (positive or negative) that are mathematically correct but practically misleading. A position held for three weeks that doubles looks like a 10,000%+ annualised IRR — impressive on paper, not a repeatable strategy signal.
• Illiquid assets like real estate or private funds require an estimated current value to calculate IRR. The quality of your IRR is only as good as the valuation you input. Use conservative, realistic figures.
• Currency effects can mask or amplify underlying asset performance. If you hold US equities and the dollar strengthened against your home currency, your IRR in local terms looks better than the underlying asset's performance — and vice versa. Always check whether your return figure is in local currency or the asset's native currency.

How to Get a Calculation You Can Actually Trust

The practical steps are straightforward:

1. Record every purchase date and price, not just the current position size. Cost basis detail is the foundation of any honest return calculation.
2. Include all cash flows — deposits, withdrawals, dividends received, and fees paid.
3. Consolidate across all accounts. A return figure that covers only one broker is a partial answer.
4. Use annualised IRR as your primary performance metric for individual positions and the overall portfolio, especially when you have made multiple purchases at different times.
5. Apply consistent currency conversion so you are comparing like with like across international holdings.

On the tax side: how you record cost basis also matters for reporting capital gains. Many jurisdictions use FIFO (First In, First Out) — meaning the oldest shares are treated as sold first — which affects which cost basis applies to a given sale. Tax rules differ significantly by country and change over time, so always verify the rules in your own jurisdiction or consult a qualified tax professional before filing.

Stop Guessing, Start Measuring

The return your broker shows you is a starting point at best. Real portfolio return calculation — the kind that accounts for every cash flow, every account, every asset class, and the actual timing of your decisions — requires a tool built for that purpose.

WealthFlow calculates IRR per asset across your entire portfolio: stocks, ETFs, investment funds tracked by ISIN and NAV, crypto, pension plans, and real estate. Because you enter your positions manually — without ever sharing broker credentials — your data stays private and you stay in control. Add your benchmark comparison to see whether your IRR is actually beating a relevant index, or use the FIFO tax-report CSV (Pro) to bring accurate cost-basis data to your accountant.

Your money deserves a more honest number than the one on your broker's dashboard. Start tracking for free at WealthFlow and see what your portfolio is actually earning.