diff --git a/buisnesslogic/src/main/java/com/plannaplan/repositories/ExchangeRepository.java b/buisnesslogic/src/main/java/com/plannaplan/repositories/ExchangeRepository.java
index 5c6be33..796625a 100644
--- a/buisnesslogic/src/main/java/com/plannaplan/repositories/ExchangeRepository.java
+++ b/buisnesslogic/src/main/java/com/plannaplan/repositories/ExchangeRepository.java
@@ -1,11 +1,20 @@
 package com.plannaplan.repositories;
 
+import java.util.Optional;
+
+import com.plannaplan.entities.Assignment;
 import com.plannaplan.entities.Exchange;
+import com.plannaplan.entities.Groups;
 
 import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Query;
+import org.springframework.data.repository.query.Param;
 import org.springframework.stereotype.Repository;
 
 @Repository
 public interface ExchangeRepository extends JpaRepository<Exchange, Long>{
+
+    @Query("FROM Exchange WHERE owned_id = ?1 AND desired_id = ?2")
+	Optional<Exchange> checkForExchange(@Param("owned_id") Assignment assignment, @Param("desired_id") Groups group);
     
 }
diff --git a/buisnesslogic/src/main/java/com/plannaplan/services/ExchangeService.java b/buisnesslogic/src/main/java/com/plannaplan/services/ExchangeService.java
index 8cd7bb0..a2f6556 100644
--- a/buisnesslogic/src/main/java/com/plannaplan/services/ExchangeService.java
+++ b/buisnesslogic/src/main/java/com/plannaplan/services/ExchangeService.java
@@ -1,6 +1,10 @@
 package com.plannaplan.services;
 
+import java.util.Optional;
+
+import com.plannaplan.entities.Assignment;
 import com.plannaplan.entities.Exchange;
+import com.plannaplan.entities.Groups;
 import com.plannaplan.repositories.ExchangeRepository;
 
 import org.springframework.beans.factory.annotation.Autowired;
@@ -19,4 +23,8 @@ public class ExchangeService {
     public Exchange save(Exchange exchange){
         return this.repo.save(exchange);
     }
+
+    public Optional<Exchange> checkForExchange(Assignment assignment, Groups group){
+        return this.repo.checkForExchange(assignment, group);
+    }
 }
diff --git a/restservice/src/main/java/com/plannaplan/controllers/ExchangeController.java b/restservice/src/main/java/com/plannaplan/controllers/ExchangeController.java
index 719f33c..e9a032c 100644
--- a/restservice/src/main/java/com/plannaplan/controllers/ExchangeController.java
+++ b/restservice/src/main/java/com/plannaplan/controllers/ExchangeController.java
@@ -68,13 +68,17 @@ public class ExchangeController extends TokenBasedController{
         }
 
         final Assignment assignmentInstance = assignment.get();
+        final Groups groupInstance = group.get();
+        final Optional<Exchange> exchangeInstance = this.exchangeService.checkForExchange(assignmentInstance, groupInstance);
 
-        if(!(assignmentInstance.getCommision().getCommisionOwner().getId() == asker.getId() && assignmentInstance.isAccepted())){
-            return new ResponseEntity<>("Some of problems appeared. Check if you have access to given assignment and if it is accepted", HttpStatus.BAD_REQUEST);
+        if(!(assignmentInstance.getCommision().getCommisionOwner().getId() == asker.getId() && assignmentInstance.isAccepted() && exchangeInstance.isEmpty())){
+            return new ResponseEntity<>("Some of problems appeared. Check if you have access to given assignment and if it is accepted or the exchange has not been already added.", HttpStatus.BAD_REQUEST);
         }
 
-        this.exchangeService.save(new Exchange(assignment.get(), group.get()));
+        this.exchangeService.save(new Exchange(assignmentInstance, groupInstance));
 
         return new ResponseEntity<>("Success", HttpStatus.OK);
     }
+
+
 }