A product can be exchanged within 30 days of the purchase, with the fiscal receipt (or the invoice for online purchases) and only if the product is in the original condition and undamaged, which will be confirmed by MY:TIME employee. These three conditions are mandatory.
If you do not have the fiscal receipt because it has been lost or the product was a gift, you can ask for a copy of the receipt in the Public Revenue Office by submitting a written request to the PRO General Management Office stating that you need a copy of the original invoice.
