Is the return number your brokerage shows you accurate?

Short answer: the number is almost certainly accurate. It is just not measuring what you think it is measuring — and it usually does not tell you which of two very different things it picked.

Here is the situation that sends people looking. You hold the same money, look at two screens, and get two different returns. One platform says you are up 8%; another says 15%. Same rand, same trades. Before you assume one of them is broken, it helps to know that there is a years-long Bogleheads thread titled "Vanguard's Personal Rate Of Return Calculation Is Embarrassing."[1] That is the sound of a sophisticated investor who suspects the figure on the screen is misleading and cannot check it. The suspicion is fair. The disagreement is real. And it is not a bug.

This piece is the practical companion to our cornerstone on how investment return is actually calculated — start there if you want the full method. Here we answer the narrower, more common question: what is the number on my specific platform's screen, and when can I trust it?

"Accurate" is the wrong question

A return figure is not a measurement like a temperature. It is the answer to a question, and there are two different questions hiding inside that one percentage:

• How good was the investment itself? — strips out when and how much you contributed.

• How well did I do, given my timing? — keeps your contributions in, because that is the part it is measuring.

The first is the time-weighted return (TWR). The second is the money-weighted return (MWR), which is what Excel calls XIRR. Neither is more "accurate" than the other. They answer different questions, and the same portfolio can produce numbers several points apart depending on which question the platform chose to answer. So the useful question is not "is this accurate?" It is "which number is this, and is it the one I want?"

What your platform is actually showing you

This is where it pays to be specific, because the platforms genuinely differ — and most of them do not label which method they used. Every claim below comes from the platform's own documentation, accessed June 2026.

Vanguard (US) shows a "personal rate of return," and it is money-weighted — an internal rate of return, in their own words "a dollar-weighted return." Vanguard even warns you not to compare it to fund or index figures, "which use a time-weighted calculation."[2] You cannot switch the method.

Fidelity (US) is the same: your "Personal Rate of Return" is money-weighted, "sometimes referred to as an internal rate of return," and customers "cannot elect the calculation methodology."[3]

Sharesight shows money-weighted by design, and is unusually honest about why — it argues in writing that time-weighted return is "less useful and potentially misleading for individual investors, who do control when cash flows in and out of their portfolios."[4]

Interactive Brokers is the exception that proves the rule: PortfolioAnalyst lets you "toggle between Time-Weighted Return (TWR) or Money-Weighted Return (MWR)."[5] If you have an IBKR account, you can watch the two numbers diverge on your own holdings — a useful exercise.

South African managers — Allan Gray, Coronation, Sygnia, Ninety One — work differently again. Their factsheets (minimum disclosure documents) publish a fund-level return: lump-sum, NAV-to-NAV, income reinvested, net of fees. That is effectively a time-weighted number for the fund. And every one of them adds the same line, almost word for word: individual investor performance may differ due to the actual investment date, the date of reinvestment, and dividend withholding tax.[6] That disclaimer is honest. It is also where they stop. It tells you the published figure is not yours, and leaves you to work out what yours is.

EasyEquities, on an individual holding, shows something simpler still: profit and loss in rand and as a percentage of cost. That is neither time- nor money-weighted and is not annualised — it is profit-on-cost, which answers "am I up or down on this position," not "what return did this earn me per year."[7]

So when two screens disagree, you are usually looking at a US-style money-weighted personal figure on one and a fund-level time-weighted figure on the other — your timing baked into the first, stripped out of the second. Both are accurate. They are answers to different questions, shown without the question.

When the displayed number is fine — and when it misleads

The number on your screen is fine for the question it answers, and only that question. A few practical rules:

If you are checking your own progress — am I on track, did my decisions serve me — a money-weighted personal return (Vanguard, Fidelity, Sharesight) is the right number. Your timing is part of your result, and money-weighted return is the only one that counts it.

If you are checking whether a fund or manager is any good — that money-weighted personal figure is the wrong tool, and quietly so. It has your contribution timing inside it, and your timing has nothing to do with the manager's skill. To judge the manager you need a time-weighted return, which is exactly what the fund factsheet quotes and exactly why it quotes it.

The misleading case is the one almost nobody notices: laying the two side by side and treating them as comparable. Your broker's personal figure next to a fund's factsheet figure is apples to oranges. They were built to answer different questions, and the gap between them can be several points wide for no reason other than when your money happened to arrive.

How wide? Our cornerstone carries a full rand example end to end. The short version: a portfolio with a R200,000 lump sum landing in August, just before a strong second half, produces a time-weighted return of 19.43% and a money-weighted return of 25.90% on identical trades — a gap of 6.46 percentage points.[8] The investment did 19.43%. The investor experienced 25.90%, because more of their capital was working during the good months. Neither number is wrong. Quoting one to answer the other's question is.

How to get the other number yourself

If your platform only shows you one number, you can compute the other. To get your money-weighted return, lay out every contribution and withdrawal with its date and run Excel's XIRR. The one discipline that matters: money leaving your wallet into the portfolio is negative; money coming back to you is positive. Get a sign wrong and XIRR returns a confident, ludicrous answer. (We cover whether XIRR is the right tool, and its sharper edges, in a companion piece.)

To get a time-weighted return you need your portfolio's value on each date money moved — harder to assemble by hand, which is the whole reason fund-level figures exist and personal ones are rare. Our MWR-vs-TWR calculator does both on the same cash-flow series, shows you the gap, and — more usefully — tells you whether the gap is even large enough to act on. For steady monthly investing it usually is not; for a big one-off lump near a market move it can be.

To conclude

The number on your brokerage screen is accurate. It is just unlabelled — one of two answers to two different questions, presented as if it were the only answer to the only question. Once you know which one you are looking at, the disagreement between your screens stops being maddening and becomes information: one screen is telling you about the investment, the other about you. What no South African platform yet gives you is a true time-weighted return per fund on your own holdings — the figure you would actually need to know whether Allan Gray, Coronation or Ninety One earned their fee. That gap is the reason we built Mintelo.