A single-entry Poland Schengen visa allows a traveler to enter Poland or the Schengen Area only once during the visa validity period. After you enter and then leave the Schengen Area, the visa cannot be used again. This type of visa is usually issued for people who plan to visit Poland for a single trip, such as tourism, visiting family, or attending a short business event. If you want to travel again after leaving, you will need to apply for a new visa.