diff --git a/library/src/calculator_functions.cpp b/library/src/calculator_functions.cpp
index 8d8a712..551d737 100644
--- a/library/src/calculator_functions.cpp
+++ b/library/src/calculator_functions.cpp
@@ -496,9 +496,22 @@ double Calculator::GetCostFromDuration(Configuration* cfg,
                         end_datetime.setTime(cs.getAllowedTimeRange().getTimeUntil());
                         return cost;
                     }
+                } else {
+                    // it might be that in such a case even prepaid ("vorkauf")
+                    // is not allowed at any moment
+                    // added e.g. for neuhauser-linsinger maschinenbau (741):
+                    // the buying of food stamps ("essensmarken") is not allowed
+                    // at any moment
+                    CalcState cs = isParkingAllowed(cfg, start_datetime);
+                    if (cs) {
+                        end_datetime = start_datetime.addSecs(durationMinutes*60);
+                        double cost = GetCostFromDuration(cfg, start_datetime, end_datetime);
+                        end_datetime = start_datetime;
+                        end_datetime.setTime(cs.getAllowedTimeRange().getTimeUntil());
+                        return cost;
+                    }
                 }
 
-                qCritical() << __PRETTY_FUNCTION__ << "NOT YET IMPLEMENTED";
                 end_datetime = QDateTime();
                 return 0;
             }