diff --git a/prometheus/app/api/routes/issue.py b/prometheus/app/api/routes/issue.py
index e58582c6..05253252 100644
--- a/prometheus/app/api/routes/issue.py
+++ b/prometheus/app/api/routes/issue.py
@@ -7,6 +7,7 @@
 from prometheus.app.services.issue_service import IssueService
 from prometheus.app.services.knowledge_graph_service import KnowledgeGraphService
 from prometheus.app.services.repository_service import RepositoryService
+from prometheus.app.services.user_service import UserService
 from prometheus.configuration.config import settings
 from prometheus.exceptions.server_exception import ServerException
 
@@ -24,19 +25,35 @@
 @requireLogin
 async def answer_issue(issue: IssueRequest, request: Request) -> Response[IssueResponse]:
     repository_service: RepositoryService = request.app.state.service["repository_service"]
+    # Fetch the repository by ID
     repository = repository_service.get_repository_by_id(issue.repository_id)
+    # Ensure the repository exists
     if not repository:
         raise ServerException(code=404, message="Repository not found")
+    # Ensure the user has access to the repository
     if settings.ENABLE_AUTHENTICATION and repository.user_id != request.state.user_id:
         raise ServerException(code=403, message="You do not have access to this repository")
 
+    # Deduct issue credit if authentication is enabled
+    user_service: UserService = request.app.state.service["user_service"]
+    if settings.ENABLE_AUTHENTICATION:
+        # Check and deduct issue credit
+        user_issue_credit = user_service.get_issue_credit(request.state.user_id)
+        if user_issue_credit <= 0:
+            raise ServerException(
+                code=403,
+                message="Insufficient issue credits. Please purchase more to continue.",
+            )
+        user_service.update_issue_credit(request.state.user_id, user_issue_credit - 1)
+
+    # Validate Dockerfile and workdir inputs
     if issue.dockerfile_content or issue.image_name:
         if issue.workdir is None:
             raise ServerException(
                 code=400,
                 message="workdir must be provided for user defined environment",
             )
-
+    # Ensure the repository is not currently being used
     if repository.is_working:
         raise ServerException(
             code=400,
diff --git a/prometheus/app/api/routes/repository.py b/prometheus/app/api/routes/repository.py
index 7aff519f..f78d44f4 100644
--- a/prometheus/app/api/routes/repository.py
+++ b/prometheus/app/api/routes/repository.py
@@ -23,7 +23,7 @@ def get_github_token(request: Request, github_token: str) -> str:
     if not settings.ENABLE_AUTHENTICATION:
         # If the user is not authenticated, raise an exception
         raise ServerException(
-            code=401, message="GitHub token is required, please provide it or log in"
+            code=400, message="GitHub token is required, please provide it or log in"
         )
     # If the user is authenticated, get the user service and fetch the token
     user_service: UserService = request.app.state.service["user_service"]
@@ -33,7 +33,7 @@ def get_github_token(request: Request, github_token: str) -> str:
     # If the token is still not available, raise an exception
     if not github_token:
         raise ServerException(
-            code=423, message="Either provide a GitHub token or set it in your user profile"
+            code=400, message="Either provide a GitHub token or set it in your user profile"
         )
     return github_token
 
diff --git a/prometheus/app/services/user_service.py b/prometheus/app/services/user_service.py
index 49fa6030..92d5c628 100644
--- a/prometheus/app/services/user_service.py
+++ b/prometheus/app/services/user_service.py
@@ -120,3 +120,33 @@ def get_user_by_id(self, user_id: int) -> Optional[User]:
         with Session(self.engine) as session:
             statement = select(User).where(User.id == user_id)
             return session.exec(statement).first()
+
+    def get_issue_credit(self, user_id: int) -> int:
+        """
+        Retrieve the issue credit of a user by their ID.
+
+        Args:
+            user_id (int): The ID of the user.
+
+        Returns:
+            int: The issue credit of the user.
+        """
+        with Session(self.engine) as session:
+            statement = select(User.issue_credit).where(User.id == user_id)
+            result = session.exec(statement).first()
+            return result
+
+    def update_issue_credit(self, user_id: int, new_issue_credit) -> None:
+        """
+        Update the issue credit of a user by their ID.
+
+        Args:
+            user_id (int): The ID of the user.
+            new_issue_credit (int): The new issue credit.
+        """
+        with Session(self.engine) as session:
+            statement = select(User).where(User.id == user_id)
+            user = session.exec(statement).first()
+            user.issue_credit = new_issue_credit
+            session.add(user)
+            session.commit()