Please click here to see the Update to our voluntary Refund Policy.
In short: 30 days, no questions asked.
Because the games are unfinished software, games in development fall under a separate refund policy. Technical issues covered by the 30 Day Money Back Guarantee do not apply to games in development. Instead, you can return the game within 30 days of your purchase - no questions asked. Your refund can be processed in GOG Wallet funds or the currency you used to make the purchase.