Here are the B2C rules for e-commerce in the EU, which are supposed to be the norm: https://europa.eu/youreurope/business/selling-in-eu/selling-... . Anything beyond that is retailer-specific. Note that this concerns all forms of remote selling, i.e. phone sales, webshops goods, but even door-to-door vending -- basically anything that does not involve the customer setting foot in your brick-and-mortar store.
> When can your customer withdraw from the contract?
If you have given all the necessary information about the right to withdraw, your customer has 14 days to withdraw from the contract - without any penalty and without having to give any reason:
For goods – this means 14 days after delivery
For services – this means 14 days after the contract was concluded
> What are your obligations after the consumer withdraws from the contract?
You must reimburse the money received from your customer (or cancel their payment) within 14 days of being notified they are withdrawing.
You may withhold this reimbursement until you have received the goods back from the customer, or at least received evidence they have actually sent them.
> Who pays what?
The Customer pays the cost of returning the goods (unless you failed to inform them of this in advance — in which case you will be liable for these costs).
Your top comment implied that it's a norm in the EU. It is not. It's very much retailer-specific.