diff --git a/src/main/java/de/infinimotion/backend/endpoint/OrderTx.java b/src/main/java/de/infinimotion/backend/endpoint/OrderTx.java
index 2c159f5..c8ffb65 100644
--- a/src/main/java/de/infinimotion/backend/endpoint/OrderTx.java
+++ b/src/main/java/de/infinimotion/backend/endpoint/OrderTx.java
@@ -6,6 +6,9 @@ import jakarta.inject.Inject;
 import jakarta.ws.rs.POST;
 import jakarta.ws.rs.Path;
 
+import java.time.Instant;
+import java.time.LocalDateTime;
+import java.time.ZoneId;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Objects;
@@ -24,6 +27,8 @@ public class OrderTx {
         int showId = orderTransaction.getTickets().stream().findAny().map(Eintrittskarte::getShow).map(Vorstellung::getId).orElse(-1);
         if (orderTransaction.getTickets().stream().anyMatch(ticket -> ticket.getShow().getId() != showId)) {
             throw new IllegalArgumentException("tickets for different show ids");
+        } else if (orderTransaction.getTickets().getFirst().getShow().getStart().isBefore(LocalDateTime.ofInstant(Instant.now(), ZoneId.systemDefault()))) {
+            throw new IllegalStateException("show already started");
         }
 
         List<String> notCancelledTicketsFilter = List.of("eq;show.id;int;" + showId, "null;order.cancelled;date;1970-01-01T00:00:00");