diff --git a/library/src/calculator_functions.cpp b/library/src/calculator_functions.cpp
index efee9fa..f4389fb 100644
--- a/library/src/calculator_functions.cpp
+++ b/library/src/calculator_functions.cpp
@@ -157,6 +157,17 @@ std::string Calculator::GetDurationFromCost(Configuration* cfg,
 
         static const bool carryOverNotSet = Utilities::isCarryOverNotSet(cfg, paymentMethodId);
         static const uint minParkingPrice = Utilities::getMinimalParkingPrice(cfg, paymentMethodId);
+        static const uint maxParkingPrice = Utilities::getMaximalParkingPrice(cfg, paymentMethodId);
+
+        if (cost < minParkingPrice) {
+            qCritical() << QString("ERROR: COST < MIN_PARKING_PRICE (%1 < %2)").arg(cost).arg(minParkingPrice);
+            return QDateTime().toString(Qt::ISODate).toStdString();
+        }
+
+        if (cost > maxParkingPrice) {
+            qCritical() << QString("WARN: COST > MAX_PARKING_PRICE (%1 > %2)").arg(cost).arg(maxParkingPrice);
+            cost = maxParkingPrice;
+        }
 
         Q_ASSERT_X(carryOverNotSet, __func__, "CARRYOVER SET (FOR KIRCHDORF)");
         Q_ASSERT_X(prepaid, __func__, "PREPAID NOT SET (FOR KIRCHDORF)");
@@ -279,6 +290,10 @@ std::string Calculator::GetDurationFromCost(Configuration* cfg,
 
                                         price += (uint)rate.pra_price;
 
+                                        if (price >= maxParkingPrice) {
+                                            price = maxParkingPrice;
+                                        }
+
                                         durationMinutes -= duration;
                                         durationMinutesNetto += duration;
                                         durationMinutesBrutto += duration;
@@ -320,10 +335,16 @@ std::string Calculator::GetDurationFromCost(Configuration* cfg,
                                     ATBPaymentRate const rate = x.second;
                                     if (rate.pra_payment_unit_id == timeRange.time_range_payment_type_id) {
                                         price += (uint)rate.pra_price;
+
+                                        if (price >= maxParkingPrice) {
+                                            price = maxParkingPrice;
+                                        }
+
                                         if (price >= cost) {
                                             end_datetime = current;
                                             // return end_datetime.toString(Qt::ISODate).toStdString();
                                         }
+
                                         break;
                                     }
                                 }