One the basis of hte Uruguayan business culture and also bureaucratic processes (in Spanish "trámites") consist of extensive use of a great amount of paper and stamping documents, receipts ("facturas") in as many places as there may be enough blank space to stamp. And each person who stamps also signs over their mark.

Do not become angry if you encounter some sort of delay when you make a purchase. This is because of propper procedures should be completed in the most accurate way. If are using your credit cards the length of time may take longer and you will be required to show your identity providing a valid document. When defining a valid document I mean a passport (or a local ID Cédula). Driver's license is not proof of identity. If your credit card has a picture of you included, you may be still asked to show a valid document in some stores.

It is common that people keep their receipts for just in case. My humble advice is to keep the bills you paid for a few months until you are certain you are not going to have its need anymore. Even when the country is becoming more computarized in terms of administration, the majority of places still follow the traditional way of being anal about paper and stamps everywhere. But please, be patient!