Foreign exchange fee (bookkeeping)

The exchange rate markup (koersopslag) is an additional fee that banks charge when converting foreign currency transactions into euros. It’s not the official exchange rate, but an extra percentage added by your bank on top of the interbank exchange rate.

From a bookkeeping point of view, it's a cost, related to currency exchange.

How it works

Interbank Exchange Rate: The real exchange rate that banks use to trade currencies between themselves
Bank’s Exchange Rate: The rate your bank offers, which includes a small markup (the koersopslag)
Your Transaction: When you pay in a foreign currency (e.g., $10), the bank converts it at their rate instead of the real interbank rate
Koersopslag Fee: The difference between the interbank rate and the rate your bank applies

Example

Suppose the real exchange rate is 1 USD = 0.961 EUR
Your $10 payment should be €9,61
Rabobank charges an extra 2% koersopslag, so the final amount becomes €9,80 (€9,61 + €0,19 koersopslag)

Why?

As a source of profit
Risk coverage
Almost all banks do this, but the percentage varies (often between 0.5% and 3%).

Alternatives

Wise (formerly TransferWise): Uses the real interbank rate + a small transparent fee
Revolut / Bunq / N26: Offer better exchange rates with low or no koersopslag (depending on account type)
Credit Cards with No FX Fees: Some business credit cards avoid these extra fees
Multi-currency bank accounts: My Alior multi-currency account has a better rate when exchanging money amongst the currencies of the account. I believe this is a general phenomenon.

How to book?

Two options:

Incorporate: Incorporate in the total cost of the associated transaction
Book separate: Book as separate cost. E.g., to account Rabobank - Costs or Rabobank - Currency exchange costs.

Both approaches have advantages and disadvantages:

Incorporate - Disadvantages

From a formal point of view, it's incorrect/inaccurate
This makes it harder to verify the correctness of the administration, as these separate "koersopslag" transactions cannot be traced back, at least not as transactions on their own
I wouldn't be able to find the exact amount of banking costs from my bookkeeping - I don't think I care about this, though.

Advantages Option 1

It shows the "effective" costs of a transaction, which is usually the main thing that is relevant for me
Less transactions in general ledger
Those separate "Koersopslag" mutations, have very little meaning to me - They are mostly clutter