diff --git a/e-invoice-domain/src/main/kotlin/net/codinux/invoicing/calculator/AmountsCalculator.kt b/e-invoice-domain/src/main/kotlin/net/codinux/invoicing/calculator/AmountsCalculator.kt
new file mode 100644
index 0000000..fe67927
--- /dev/null
+++ b/e-invoice-domain/src/main/kotlin/net/codinux/invoicing/calculator/AmountsCalculator.kt
@@ -0,0 +1,44 @@
+package net.codinux.invoicing.calculator
+
+import net.codinux.invoicing.mapper.MustangMapper
+import net.codinux.invoicing.model.Invoice
+import net.codinux.invoicing.model.TotalAmounts
+import org.mustangproject.ZUGFeRD.IExportableTransaction
+import org.mustangproject.ZUGFeRD.TransactionCalculator
+import java.math.BigDecimal
+
+open class AmountsCalculator {
+
+    protected open val mapper by lazy { MustangMapper() } // lazy to avoid circular dependency creation with MustangMapper
+
+
+    open fun calculateTotalAmounts(invoice: Invoice) =
+        calculateTotalAmounts(mapper.mapToTransaction(invoice))
+
+    open fun calculateTotalAmounts(invoice: IExportableTransaction): TotalAmounts {
+        val calculator = MustangTransactionCalculator(invoice)
+
+        return TotalAmounts(
+            lineTotalAmount = calculator.lineTotalAmount,
+            chargeTotalAmount = calculator.chargeTotal,
+            allowanceTotalAmount = calculator.allowanceTotal,
+            taxBasisTotalAmount = calculator.taxBasisTotalAmount,
+            taxTotalAmount = calculator.taxTotalAmount,
+            grandTotalAmount = calculator.grandTotal,
+            totalPrepaidAmount = calculator.totalPrepaidAmount,
+            duePayableAmount = calculator.duePayableAmount
+        )
+    }
+
+
+    protected open class MustangTransactionCalculator(invoice: IExportableTransaction): TransactionCalculator(invoice) {
+        val lineTotalAmount: BigDecimal = this.total
+
+        val taxBasisTotalAmount: BigDecimal = this.taxBasis
+        val taxTotalAmount: BigDecimal by lazy { this.getGrandTotal().subtract(this.taxBasis) }
+
+        val totalPrepaidAmount: BigDecimal = this.totalPrepaid
+        val duePayableAmount: BigDecimal by lazy { this.getGrandTotal().subtract(this.totalPrepaid) }
+    }
+
+}
\ No newline at end of file
diff --git a/e-invoice-domain/src/main/kotlin/net/codinux/invoicing/mapper/MustangMapper.kt b/e-invoice-domain/src/main/kotlin/net/codinux/invoicing/mapper/MustangMapper.kt
index c1177d8..b1114e1 100644
--- a/e-invoice-domain/src/main/kotlin/net/codinux/invoicing/mapper/MustangMapper.kt
+++ b/e-invoice-domain/src/main/kotlin/net/codinux/invoicing/mapper/MustangMapper.kt
@@ -1,5 +1,6 @@
 package net.codinux.invoicing.mapper
 
+import net.codinux.invoicing.calculator.AmountsCalculator
 import net.codinux.invoicing.model.AmountAdjustments
 import net.codinux.invoicing.model.ChargeOrAllowance
 import net.codinux.invoicing.model.InvoiceItem
@@ -13,7 +14,9 @@ import java.time.LocalDate
 import java.time.ZoneId
 import java.util.*
 
-open class MustangMapper {
+open class MustangMapper(
+    protected open val calculator: AmountsCalculator = AmountsCalculator()
+) {
 
     open fun mapToTransaction(invoice: net.codinux.invoicing.model.Invoice): IExportableTransaction = Invoice().apply {
         this.number = invoice.invoiceNumber
@@ -33,6 +36,10 @@ open class MustangMapper {
             adjustments.charges.forEach { this.addCharge(mapCharge(it)) }
             adjustments.allowances.forEach { this.addAllowance(mapAllowance(it)) }
         }
+
+        if (invoice.totalAmounts == null) {
+            invoice.totalAmounts = calculator.calculateTotalAmounts(this)
+        }
     }
 
     open fun mapParty(party: Party): TradeParty = TradeParty(
@@ -95,6 +102,8 @@ open class MustangMapper {
         buyerReference = invoice.referenceNumber,
 
         amountAdjustments = mapAmountAdjustments(invoice),
+
+        totalAmounts = calculator.calculateTotalAmounts(invoice)
     )
 
     open fun mapParty(party: TradeParty) = Party(