Looking up a past portfolio value: how portfolio time travel works

To reconstruct what your portfolio was worth on a specific date in the past, you need two things: which positions you actually held on that date, and the closing price plus exchange rate of every position on that exact date — a CSV export of your transactions only gives you the first part.

A simple question with a not-so-simple answer

“What was my portfolio worth on 1 January?” or “how much was I up on the day I made that big purchase?” — it sounds like a basic question, but DEGIRO’s own interface mainly shows your current positions and the full history of transactions. To reconstruct a value on one specific date in the past, you need to combine two things that aren’t available together anywhere in a simple overview.

What you need to reconstruct a date in the past

1. Which positions you actually held on that date. That’s not your current portfolio, but the sum of all buy and sell transactions up to that date — including any interim sales you may have since forgotten about (that happens to almost everyone).
2. The closing price and exchange rate of every position on that exact date. Not today’s price, and not an average — the price as it stood at that specific moment.

A CSV export of your transactions only gives you the first part. The second part — historical prices and exchange rates per day — you have to look up separately and match to each position by hand. We’ve seen users try this manually in a spreadsheet — and after the first stock split or name change in their portfolio, the numbers stop adding up.

Note: this assumes a position that hasn’t changed. If the stock underwent a split, ticker change or merger in the meantime, a simple sum of purchase and sale quantities no longer holds — you then need to correct for the ratio of that corporate action.

Worked example

Say you bought 10 shares of stock X on 15 January for $150 each, and bought 5 more on 10 May at $180 each. You want to know what this position was worth on 1 June.

On that date you held 15 shares (10 + 5). Stock X closed on 1 June at $175, at an exchange rate of $1.08 per euro.

15 × $175 = $2,625 $2,625 ÷ 1.08 ≈ €2,430.56

That’s already for a single position on a single date. Manageable with a calculator. Do this for a portfolio of ten or twenty positions, across multiple dates you want to compare, and beyond a handful of positions it genuinely becomes impossible to do by hand without mistakes.

What this is used for

• Comparing from a specific starting point — for example your return since a particular deposit, independent of your full history (see calculating your DEGIRO return).
• Assessing a decision after the fact — how your portfolio looked just before or after a large purchase or sale. For a position you sold, a what-if analysis of sold positions takes this a step further.
• Comparing periods — for example how your asset allocation six months ago differed from today.
• Your tax return — in the Netherlands, your portfolio value on 1 January is what counts for Box 3; see the DEGIRO annual statement for your tax return.

How ClearAnalyser calculates this for you

ClearAnalyser reconstructs your entire portfolio — including cash position and asset allocation — for any date in the past, automatically and based on your live transaction history. No manual price lookups needed. How other tools compare is shown in the DEGIRO portfolio tracker comparison.

Sources: Euro foreign exchange reference rates — European Central Bank