---
title: Return purchase order calculator
slug: commerce-connect-13/docs/calculating-orders-return-purchase-order-calculator
docTags: 
createdAt: 2026-07-23T09:44:49.000Z
---

- **Total** – Calculates the total of all return order forms in a purchase order.

```csharp
public void GetTotal(IPurchaseOrder purchaseOrder, IReturnPurchaseOrderCalculator returnPurchaseOrderCalculator)
       {
         var total = returnPurchaseOrderCalculator.GetTotal(purchaseOrder);
         Debug.WriteLine("Total for return order '{0}': {1}", purchaseOrder.OrderLink.OrderGroupId, total);
       }
```

- **SubTotal** – Calculates the subtotal of all return order forms in a purchase order.

```csharp
public void GetSubTotal(IPurchaseOrder purchaseOrder, IReturnPurchaseOrderCalculator returnPurchaseOrderCalculator)
       {
         var subTotal = returnPurchaseOrderCalculator.GetSubTotal(purchaseOrder);
         Debug.WriteLine("Subtotal for return order '{0}': {1}", purchaseOrder.OrderLink.OrderGroupId, subTotal);
       }
```

- **ShippingSubTotal** – Calculates the shipping subtotal of all return order forms in a purchase order.

```csharp
public void GetShippingSubTotal(IPurchaseOrder purchaseOrder, IReturnPurchaseOrderCalculator returnPurchaseOrderCalculator)
       {
         var shippingSubTotal = returnPurchaseOrderCalculator.GetShippingSubTotal(purchaseOrder);
         Debug.WriteLine("Shipping subtotal for return order '{0}': {1}", purchaseOrder.OrderLink.OrderGroupId, shippingSubTotal);
       }
```

## Change the default calculation

By inheriting from the default implementation of the interface, DefaultReturnPurchaseOrderCalculator, you can override the calculations. Just override one or more methods in DefaultReturnPurchaseOrderCalculator.

```csharp
public class ReturnPurchaseOrderCalculatorOverridingDefault : DefaultReturnPurchaseOrderCalculator
      {
        public ReturnPurchaseOrderCalculatorOverridingDefault(IReturnOrderFormCalculator returnOrderFormCalculator)
          : base(returnOrderFormCalculator)
          { }
        protected override Money GetOrderDiscountTotal(IPurchaseOrder purchaseOrder)
          {
            return new Money(0, purchaseOrder.Currency);
          }
        protected override Money CalculateTotal(IPurchaseOrder purchaseOrder)
          {
            return new Money(0, purchaseOrder.Currency);
          }
        protected override Money CalculateSubTotal(IPurchaseOrder purchaseOrder)
          {
            return new Money(0, purchaseOrder.Currency);
          }
        protected override Money CalculateShippingSubTotal(IPurchaseOrder purchaseOrder)
          {
            return new Money(0, purchaseOrder.Currency);
          }
        protected override IEnumerable<IReturnOrderForm> GetActiveReturnForms(IPurchaseOrder purchaseOrder)
          {
            return new List<IReturnOrderForm>();
          }
      }
```

## Change the default validation

The default implementation validates that the totals are not negative after the calculation. To change the behavior, override the ValidateTotal, ValidateSubTotal and ValidateShippingSubTotal methods.

```csharp
public class ReturnPurchaseOrderCalculatorOverridingDefault : DefaultReturnPurchaseOrderCalculator
      {
        public ReturnPurchaseOrderCalculatorOverridingDefault(IReturnOrderFormCalculator returnOrderFormCalculator)
          : base(returnOrderFormCalculator)
          { }
        protected override void ValidateTotal(Money money)
          {
            if (money.Amount <= 0)
              {
                throw new ValidationException("Order total must be greater than 0");
              }
          }
        protected override void ValidateSubTotal(Money money)
          {
            if (money.Amount <= 0)
              {
                throw new ValidationException("Order subtotal must be greater than 0");
              }
          }
        protected override void ValidateShippingSubTotal(Money money)
          {
            if (money.Amount <= 0)
              {
                throw new ValidationException("Shipping subtotal must be greater than 0");
              }
          }
      }
```