The retailer wants me to pay return shipping. Is that allowed?

Two regimes, two outcomes

A return falls legally under one of two regimes, and which one applies decides entirely who pays.

Withdrawal. You buy at a distance, receive the product and decide within fourteen days that you do not want it. That is the right of rescission in article 6:230o of the Dutch Civil Code. You do not have to give a reason. The price you pay for that is in article 6:230s(2): the consumer bears the direct costs of returning the goods, unless the trader has failed to inform the consumer that they must bear those costs.

Non-conformity. What was delivered does not answer to the contract: a different size from the one ordered, a defective unit, something that does not do what the product page promised. That is article 7:17. You are not withdrawing, you are demanding performance. And then article 7:21(2) applies: the costs of performing the obligations referred to in paragraph 1 may not be charged to the buyer, and paragraph 7: the seller takes the goods back at its own expense.

Why retailers do not make the distinction

To a retailer, every return is simply a return. The returns portal generates a label, the label costs money, and that amount is deducted from the refund. Whether the parcel is coming back because the customer had second thoughts or because the warehouse picked the wrong box is invisible to that system.

The result is that consumers who did nothing wrong systematically help pay for the seller's mistake. On a single parcel it is six or eight euros, and that is precisely why almost everybody lets it go.

What "the retailer never told me" is worth

The exception in article 6:230s(2) is sharper than it looks. If the retailer did not tell you before the sale was concluded that the return costs are yours, you do not bear them. That disclosure belongs to the pre-contractual information required by article 6:230m(1). A sentence buried deep in the terms and conditions has repeatedly been held insufficient in case law.

In practice: look at the product page, at the checkout and in the order confirmation. If it appears nowhere, there is a real basis for reclaiming the costs, even on an ordinary withdrawal.

Offsetting is not automatically allowed

A retailer that withholds return costs in a non-conformity case is in effect refunding less than it owes. The amount withheld was then paid without legal ground and can be reclaimed under article 6:203 as an undue payment. That is a claim in its own right, separate from the purchase price.

What their terms and conditions say about this does not matter

Almost every retailer has a clause putting return costs on the customer without distinguishing the reason. In a consumer sale, article 7:6(1) does not permit departure to the buyer's detriment from sections 1 to 7 of title 1 of book 7. A clause that does so anyway is voidable. It is written there, it is not legally valid, and it works only for as long as nobody challenges it.

What you can do

1. First establish which regime your case falls under. Wrong, broken or not as described is non-conformity, and then the costs are not yours.
2. Record what was delivered. Photographs of the product and of the shipping label, and the product page as it looked when you ordered.
3. State in writing that you are relying on non-conformity and not on your cooling-off period. That difference decides the outcome and it is often absent from the returns form.
4. Pay for the return shipment first if you must, but keep the proof. It can be reclaimed afterwards.