diff --git a/office-alexander-logistics-app/src/main/java/com/alexanderlogistics/einvoice/KSeFInvoiceLineBuilder.java b/office-alexander-logistics-app/src/main/java/com/alexanderlogistics/einvoice/KSeFInvoiceLineBuilder.java
index 3c9ce7f..af42f52 100644
--- a/office-alexander-logistics-app/src/main/java/com/alexanderlogistics/einvoice/KSeFInvoiceLineBuilder.java
+++ b/office-alexander-logistics-app/src/main/java/com/alexanderlogistics/einvoice/KSeFInvoiceLineBuilder.java
@@ -286,34 +286,49 @@ public class KSeFInvoiceLineBuilder {
             Map<TaxCode, NetVatPair> aggregates,
             BigDecimal grossTotal) {
 
-        Element elementAdnotacje = model.findOrCreateChildNode(elementFa, EInvoiceNS.KSEF, "Adnotacje");
+        // Aggregate by target XML field name, because multiple TaxCodes
+        // can map to the same summary field (e.g. CARGO_0, CARGO_0MR,
+        // CARGO_023 all target P_13_6_1).
+        Map<String, BigDecimal> netByField = new java.util.LinkedHashMap<>();
+        Map<String, BigDecimal> vatByField = new java.util.LinkedHashMap<>();
+        boolean reverseCharge = false;
 
         for (Map.Entry<TaxCode, NetVatPair> entry : aggregates.entrySet()) {
             TaxCode taxCode = entry.getKey();
             NetVatPair pair = entry.getValue();
 
-            // Net summary field (always present)
-            String netField = taxCode.getNetSummaryField();
-            Element netElement = model.findOrCreateChildNode(elementFa, EInvoiceNS.KSEF, netField);
-            netElement.setTextContent(format(pair.net));
-            logger.info("│   ├──  set " + netField + " = " + format(pair.net));
+            netByField.merge(taxCode.getNetSummaryField(), pair.net, BigDecimal::add);
 
-            // VAT summary field (only for taxable codes)
             if (taxCode.hasVat()) {
-                String vatField = taxCode.getVatSummaryField();
-                Element vatElement = model.findOrCreateChildNode(elementFa, EInvoiceNS.KSEF, vatField);
-                vatElement.setTextContent(format(pair.vat));
-                logger.info("│   ├──  set " + vatField + " = " + format(pair.vat));
+                vatByField.merge(taxCode.getVatSummaryField(), pair.vat, BigDecimal::add);
             }
 
-            // Set P_18
-            Element p18Element = model.findOrCreateChildNode(elementAdnotacje, EInvoiceNS.KSEF, "P_18");
-            p18Element.setTextContent(taxCode.getP18Value());
-            logger.info("│   ├──  set P_18 = " + taxCode.getP18Value());
-
+            if ("1".equals(taxCode.getP18Value())) {
+                reverseCharge = true;
+            }
         }
 
-        // P_15 - gross total of the entire invoice (always present)
+        // Write net summary fields (P_13_x)
+        for (Map.Entry<String, BigDecimal> entry : netByField.entrySet()) {
+            Element netElement = model.findOrCreateChildNode(elementFa, EInvoiceNS.KSEF, entry.getKey());
+            netElement.setTextContent(format(entry.getValue()));
+            logger.info("│   ├──  set " + entry.getKey() + " = " + format(entry.getValue()));
+        }
+
+        // Write VAT summary fields (P_14_x)
+        for (Map.Entry<String, BigDecimal> entry : vatByField.entrySet()) {
+            Element vatElement = model.findOrCreateChildNode(elementFa, EInvoiceNS.KSEF, entry.getKey());
+            vatElement.setTextContent(format(entry.getValue()));
+            logger.info("│   ├──  set " + entry.getKey() + " = " + format(entry.getValue()));
+        }
+
+        // P_18 - reverse charge flag
+        Element elementAdnotacje = model.findOrCreateChildNode(elementFa, EInvoiceNS.KSEF, "Adnotacje");
+        Element p18Element = model.findOrCreateChildNode(elementAdnotacje, EInvoiceNS.KSEF, "P_18");
+        p18Element.setTextContent(reverseCharge ? "1" : "2");
+        logger.info("│   ├──  set P_18 = " + (reverseCharge ? "1" : "2"));
+
+        // P_15 - gross total
         Element p15 = model.findOrCreateChildNode(elementFa, EInvoiceNS.KSEF, "P_15");
         p15.setTextContent(format(grossTotal));
         logger.info("│   ├──  set P_15 = " + format(grossTotal));
diff --git a/office-alexander-logistics-app/src/test/java/com/alexanderlogistics/ksef/api/KSeFAdapterTest.java b/office-alexander-logistics-app/src/test/java/com/alexanderlogistics/ksef/api/KSeFAdapterTest.java
index 5a8d850..a34bdb8 100644
--- a/office-alexander-logistics-app/src/test/java/com/alexanderlogistics/ksef/api/KSeFAdapterTest.java
+++ b/office-alexander-logistics-app/src/test/java/com/alexanderlogistics/ksef/api/KSeFAdapterTest.java
@@ -491,6 +491,86 @@ public class KSeFAdapterTest {
                 "Unknown CargoSoft VAT code must raise a PluginException");
     }
 
+    /**
+     * Multiple 0% KR codes (023, 0, 0MR) on the same invoice in USD.
+     * <p>
+     * Regression test for the summary aggregation bug: all three CargoSoft
+     * codes map to {@code P_13_6_1}. Before the fix, only the last code's
+     * amount survived because {@code setTextContent} overwrote the previous
+     * value instead of summing. Expected: {@code P_13_6_1 = 2640.00}
+     * (1515 + 340 + 785).
+     */
+    @Test
+    @DisplayName("Test Multiple 0% KR Codes aggregate into P_13_6_1 (USD)")
+    public void testMultipleZeroRateCodes() throws Exception {
+        logger.info("==> Test: Multiple 0% KR Codes");
+
+        ItemCollection workitem = new ItemCollection();
+        workitem.setItemValue("invoice.number", "FV/2026/7795");
+        workitem.setItemValue("invoice.date", LocalDate.of(2026, 5, 22));
+        workitem.setItemValue("invoice.duedate", LocalDate.of(2026, 6, 21));
+        workitem.setItemValue("invoice.performancedate", LocalDate.of(2026, 5, 21));
+        workitem.setItemValue("invoice.currency", "USD");
+        workitem.setItemValue("invoice.rate", 0.2724); // CargoSoft format
+        workitem.setItemValue("invoice.correction", "false");
+        workitem.setItemValue("invoice.CorrectionInvoiceNumber", "");
+        workitem.setItemValue("partner.id", "BP-001");
+        workitem.setItemValue("partner.vat", "PL1234567890");
+
+        List<Object> childItems = new ArrayList<>();
+
+        // Position 1: code "023" -> 0 KR -> P_13_6_1
+        ItemCollection lineItem1 = new ItemCollection()
+                .setItemValue("numpos", "1")
+                .setItemValue("datev.text", "Fracht morski")
+                .setItemValue("billingtext", "Usługa spedycyjna: Fracht morski, + ubezpieczenie")
+                .setItemValue("datev.umsatz", 1515.00)
+                .setItemValue("datev.vatrate", 0.0)
+                .setItemValue("cargosoft.vat.code", "023");
+        childItems.add(lineItem1.getAllItems());
+
+        // Position 2: code "0" -> 0 KR -> P_13_6_1
+        ItemCollection lineItem2 = new ItemCollection()
+                .setItemValue("numpos", "2")
+                .setItemValue("datev.text", "THC")
+                .setItemValue("billingtext", "Usługa spedycyjna: THC")
+                .setItemValue("datev.umsatz", 340.00)
+                .setItemValue("datev.vatrate", 0.0)
+                .setItemValue("cargosoft.vat.code", "0");
+        childItems.add(lineItem2.getAllItems());
+
+        // Position 3: code "0MR" -> 0 KR -> P_13_6_1
+        ItemCollection lineItem3 = new ItemCollection()
+                .setItemValue("numpos", "3")
+                .setItemValue("datev.text", "Transport intermodalny")
+                .setItemValue("billingtext", "Usługa spedycyjna:, transport intermodalny")
+                .setItemValue("datev.umsatz", 785.00)
+                .setItemValue("datev.vatrate", 0.0)
+                .setItemValue("cargosoft.vat.code", "0MR");
+        childItems.add(lineItem3.getAllItems());
+
+        workitem.setItemValue("_childitems", childItems);
+
+        when(businessPartnerService.getBusinessPartnerByID("BP-001"))
+                .thenReturn(businessPartner);
+
+        FileData xmlTemplate = loadTemplateFromResources(TEMPLATE_FILE);
+
+        adapter.updateEInvoice(xmlTemplate, workitem);
+
+        assertNotNull(xmlTemplate.getContent(), "XML content should not be null after update");
+        assertTrue(xmlTemplate.getContent().length > 0, "XML content should not be empty");
+
+        // Verify that P_13_6_1 contains the SUM of all three positions
+        String xml = new String(xmlTemplate.getContent(), "UTF-8");
+        assertTrue(xml.contains("<P_13_6_1>2640.00</P_13_6_1>"),
+                "P_13_6_1 must be the sum of all 0%KR positions (1515 + 340 + 785 = 2640.00) but was not");
+        assertTrue(xml.contains("<P_15>2640.00</P_15>"),
+                "P_15 must equal the gross total (2640.00) but was not");
+
+        writeOutputToResources(xmlTemplate, "invoice-multiple-zero-rate-codes.xml");
+    }
+
     // ── Helper methods ──────────────────────────────────────────────
 
     /**
diff --git a/office-alexander-logistics-app/src/test/resources/ksef/output/invoice-eu-service-np.xml b/office-alexander-logistics-app/src/test/resources/ksef/output/invoice-eu-service-np.xml
index 703d868..bf5d589 100644
--- a/office-alexander-logistics-app/src/test/resources/ksef/output/invoice-eu-service-np.xml
+++ b/office-alexander-logistics-app/src/test/resources/ksef/output/invoice-eu-service-np.xml
@@ -6,7 +6,7 @@
    <Naglowek>
       <KodFormularza kodSystemowy="FA (3)" wersjaSchemy="1-0E">FA</KodFormularza>
       <WariantFormularza>3</WariantFormularza>
-      <DataWytworzeniaFa>2026-05-14T09:50:45.122365080Z</DataWytworzeniaFa>
+      <DataWytworzeniaFa>2026-05-28T19:15:59.290135Z</DataWytworzeniaFa>
       <SystemInfo>Imixs eInvoice</SystemInfo>
    </Naglowek>
    <Podmiot1>
@@ -42,7 +42,7 @@
       <P_1>2025-02-10</P_1>
       <P_1M>Szczecin</P_1M>
       <P_2>FV/2025/7470</P_2>
-      <P_6>2026-05-14</P_6>
+      <P_6>2026-05-28</P_6>
       <P_13_9>4620.00</P_13_9>
       <P_15>4620.00</P_15>
       <KursWalutyZ>0.2326</KursWalutyZ>
diff --git a/office-alexander-logistics-app/src/test/resources/ksef/output/invoice-mixed-rates.xml b/office-alexander-logistics-app/src/test/resources/ksef/output/invoice-mixed-rates.xml
index d7364b1..863a3eb 100644
--- a/office-alexander-logistics-app/src/test/resources/ksef/output/invoice-mixed-rates.xml
+++ b/office-alexander-logistics-app/src/test/resources/ksef/output/invoice-mixed-rates.xml
@@ -6,7 +6,7 @@
    <Naglowek>
       <KodFormularza kodSystemowy="FA (3)" wersjaSchemy="1-0E">FA</KodFormularza>
       <WariantFormularza>3</WariantFormularza>
-      <DataWytworzeniaFa>2026-05-14T09:50:45.516800880Z</DataWytworzeniaFa>
+      <DataWytworzeniaFa>2026-05-28T19:15:59.433548Z</DataWytworzeniaFa>
       <SystemInfo>Imixs eInvoice</SystemInfo>
    </Naglowek>
    <Podmiot1>
@@ -42,7 +42,7 @@
       <P_1>2025-02-10</P_1>
       <P_1M>Szczecin</P_1M>
       <P_2>FV/2025/7471</P_2>
-      <P_6>2026-05-14</P_6>
+      <P_6>2026-05-28</P_6>
       <P_13_1>3960.00</P_13_1>
       <P_14_1>910.80</P_14_1>
       <P_13_6_1>14040.00</P_13_6_1>
diff --git a/office-alexander-logistics-app/src/test/resources/ksef/output/invoice-multiple-zero-rate-codes.xml b/office-alexander-logistics-app/src/test/resources/ksef/output/invoice-multiple-zero-rate-codes.xml
new file mode 100644
index 0000000..0aa21e4
--- /dev/null
+++ b/office-alexander-logistics-app/src/test/resources/ksef/output/invoice-multiple-zero-rate-codes.xml
@@ -0,0 +1,124 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Faktura xmlns="http://crd.gov.pl/wzor/2025/06/25/13775/"
+         xmlns:etd="http://crd.gov.pl/xml/schematy/dziedzinowe/mf/2022/01/05/eD/DefinicjeTypy/"
+         xmlns:xsd="http://www.w3.org/2001/XMLSchema"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+   <Naglowek>
+      <KodFormularza kodSystemowy="FA (3)" wersjaSchemy="1-0E">FA</KodFormularza>
+      <WariantFormularza>3</WariantFormularza>
+      <DataWytworzeniaFa>2026-05-28T19:15:59.040792Z</DataWytworzeniaFa>
+      <SystemInfo>Imixs eInvoice</SystemInfo>
+   </Naglowek>
+   <Podmiot1>
+      <PrefiksPodatnika>PL</PrefiksPodatnika>
+      <DaneIdentyfikacyjne>
+         <NIP>9552521552</NIP>
+         <Nazwa>ALEXANDER GLOBAL LOGISTICS POLAND sp. z o.o.</Nazwa>
+      </DaneIdentyfikacyjne>
+      <Adres>
+         <KodKraju>PL</KodKraju>
+         <AdresL1>ul. Gdańska 36, 70-660 Szczecin</AdresL1>
+      </Adres>
+      <DaneKontaktowe>
+         <Email>MBudas@alexander-logistics.com</Email>
+      </DaneKontaktowe>
+   </Podmiot1>
+   <Podmiot2>
+      <DaneIdentyfikacyjne>
+         <NIP>1234567890</NIP>
+         <Nazwa>Test Sp. z o.o.</Nazwa>
+      </DaneIdentyfikacyjne>
+      <Adres>
+         <KodKraju>PL</KodKraju>
+         <AdresL1>ul. Testowa 1</AdresL1>
+         <AdresL2>00-001 Warszawa</AdresL2>
+      </Adres>
+      <NrKlienta>D-12345</NrKlienta>
+      <JST>2</JST>
+      <GV>2</GV>
+   </Podmiot2>
+   <Fa>
+      <KodWaluty>USD</KodWaluty>
+      <P_1>2026-05-22</P_1>
+      <P_1M>Szczecin</P_1M>
+      <P_2>FV/2026/7795</P_2>
+      <P_6>2026-05-21</P_6>
+      <P_13_6_1>2640.00</P_13_6_1>
+      <P_15>2640.00</P_15>
+      <KursWalutyZ>3.6711</KursWalutyZ>
+      <Adnotacje>
+         <P_16>2</P_16>
+         <P_17>2</P_17>
+         <P_18>2</P_18>
+         <P_18A>2</P_18A>
+         <Zwolnienie>
+            <P_19N>1</P_19N>
+         </Zwolnienie>
+         <NoweSrodkiTransportu>
+            <P_22N>1</P_22N>
+         </NoweSrodkiTransportu>
+         <P_23>2</P_23>
+         <PMarzy>
+            <P_PMarzyN>1</P_PMarzyN>
+         </PMarzy>
+      </Adnotacje>
+      <RodzajFaktury>VAT</RodzajFaktury>
+      <FaWiersz>
+         <NrWierszaFa>1</NrWierszaFa>
+         <P_7>Usługa spedycyjna: Fracht morski, + ubezpieczenie</P_7>
+         <P_8A>szt.</P_8A>
+         <P_8B>1.00</P_8B>
+         <P_9A>1515.00</P_9A>
+         <P_11>1515.00</P_11>
+         <P_11A>1515.00</P_11A>
+         <P_11Vat>0.00</P_11Vat>
+         <P_12>0 KR</P_12>
+      </FaWiersz>
+      <FaWiersz>
+         <NrWierszaFa>2</NrWierszaFa>
+         <P_7>Usługa spedycyjna: THC</P_7>
+         <P_8A>szt.</P_8A>
+         <P_8B>1.00</P_8B>
+         <P_9A>340.00</P_9A>
+         <P_11>340.00</P_11>
+         <P_11A>340.00</P_11A>
+         <P_11Vat>0.00</P_11Vat>
+         <P_12>0 KR</P_12>
+      </FaWiersz>
+      <FaWiersz>
+         <NrWierszaFa>3</NrWierszaFa>
+         <P_7>Usługa spedycyjna:, transport intermodalny</P_7>
+         <P_8A>szt.</P_8A>
+         <P_8B>1.00</P_8B>
+         <P_9A>785.00</P_9A>
+         <P_11>785.00</P_11>
+         <P_11A>785.00</P_11A>
+         <P_11Vat>0.00</P_11Vat>
+         <P_12>0 KR</P_12>
+      </FaWiersz>
+      <Platnosc>
+         <TerminPlatnosci>
+            <Termin>2026-06-21</Termin>
+         </TerminPlatnosci>
+         <FormaPlatnosci>6</FormaPlatnosci>
+         <RachunekBankowy>
+            <NrRB>PL79116022020000000654306674</NrRB>
+            <SWIFT>BIGBPLPWXXX</SWIFT>
+            <NazwaBanku>Bank Millennium S.A.</NazwaBanku>
+            <OpisRachunku>Konto PLN</OpisRachunku>
+         </RachunekBankowy>
+         <RachunekBankowy>
+            <NrRB>PL16116022020000000654910469</NrRB>
+            <SWIFT>BIGBPLPWXXX</SWIFT>
+            <NazwaBanku>Bank Millennium S.A.</NazwaBanku>
+            <OpisRachunku>Konto EUR</OpisRachunku>
+         </RachunekBankowy>
+         <RachunekBankowy>
+            <NrRB>PL72116022020000000654911595</NrRB>
+            <SWIFT>BIGBPLPWXXX</SWIFT>
+            <NazwaBanku>Bank Millennium S.A.</NazwaBanku>
+            <OpisRachunku>Konto USD</OpisRachunku>
+         </RachunekBankowy>
+      </Platnosc>
+   </Fa>
+</Faktura>
diff --git a/office-alexander-logistics-app/src/test/resources/ksef/output/invoice-np.xml b/office-alexander-logistics-app/src/test/resources/ksef/output/invoice-np.xml
index a0dcd88..7342d97 100644
--- a/office-alexander-logistics-app/src/test/resources/ksef/output/invoice-np.xml
+++ b/office-alexander-logistics-app/src/test/resources/ksef/output/invoice-np.xml
@@ -6,7 +6,7 @@
    <Naglowek>
       <KodFormularza kodSystemowy="FA (3)" wersjaSchemy="1-0E">FA</KodFormularza>
       <WariantFormularza>3</WariantFormularza>
-      <DataWytworzeniaFa>2026-05-14T09:50:45.478749958Z</DataWytworzeniaFa>
+      <DataWytworzeniaFa>2026-05-28T19:15:59.394284Z</DataWytworzeniaFa>
       <SystemInfo>Imixs eInvoice</SystemInfo>
    </Naglowek>
    <Podmiot1>
@@ -42,7 +42,7 @@
       <P_1>2025-02-10</P_1>
       <P_1M>Szczecin</P_1M>
       <P_2>FV/2025/001</P_2>
-      <P_6>2026-05-14</P_6>
+      <P_6>2026-05-28</P_6>
       <P_13_9>10000.00</P_13_9>
       <P_15>10000.00</P_15>
       <Adnotacje>
diff --git a/office-alexander-logistics-app/src/test/resources/ksef/output/invoice-npt.xml b/office-alexander-logistics-app/src/test/resources/ksef/output/invoice-npt.xml
index 2a86850..c56d1ad 100644
--- a/office-alexander-logistics-app/src/test/resources/ksef/output/invoice-npt.xml
+++ b/office-alexander-logistics-app/src/test/resources/ksef/output/invoice-npt.xml
@@ -6,7 +6,7 @@
    <Naglowek>
       <KodFormularza kodSystemowy="FA (3)" wersjaSchemy="1-0E">FA</KodFormularza>
       <WariantFormularza>3</WariantFormularza>
-      <DataWytworzeniaFa>2026-05-14T09:50:45.408813197Z</DataWytworzeniaFa>
+      <DataWytworzeniaFa>2026-05-28T19:15:59.342086Z</DataWytworzeniaFa>
       <SystemInfo>Imixs eInvoice</SystemInfo>
    </Naglowek>
    <Podmiot1>
@@ -42,7 +42,7 @@
       <P_1>2025-02-10</P_1>
       <P_1M>Szczecin</P_1M>
       <P_2>FV/2025/001</P_2>
-      <P_6>2026-05-14</P_6>
+      <P_6>2026-05-28</P_6>
       <P_13_8>10000.00</P_13_8>
       <P_15>10000.00</P_15>
       <Adnotacje>
diff --git a/office-alexander-logistics-app/src/test/resources/ksef/output/invoice-simple.xml b/office-alexander-logistics-app/src/test/resources/ksef/output/invoice-simple.xml
index 00f7f7f..6d61c21 100644
--- a/office-alexander-logistics-app/src/test/resources/ksef/output/invoice-simple.xml
+++ b/office-alexander-logistics-app/src/test/resources/ksef/output/invoice-simple.xml
@@ -6,7 +6,7 @@
    <Naglowek>
       <KodFormularza kodSystemowy="FA (3)" wersjaSchemy="1-0E">FA</KodFormularza>
       <WariantFormularza>3</WariantFormularza>
-      <DataWytworzeniaFa>2026-05-14T09:50:45.613224263Z</DataWytworzeniaFa>
+      <DataWytworzeniaFa>2026-05-28T19:15:59.512152Z</DataWytworzeniaFa>
       <SystemInfo>Imixs eInvoice</SystemInfo>
    </Naglowek>
    <Podmiot1>
@@ -42,7 +42,7 @@
       <P_1>2025-02-10</P_1>
       <P_1M>Szczecin</P_1M>
       <P_2>FV/2025/001</P_2>
-      <P_6>2026-05-14</P_6>
+      <P_6>2026-05-28</P_6>
       <P_13_1>10000.00</P_13_1>
       <P_14_1>2300.00</P_14_1>
       <P_15>12300.00</P_15>
diff --git a/office-alexander-logistics-app/src/test/resources/ksef/output/test-korrekturrechnung.xml b/office-alexander-logistics-app/src/test/resources/ksef/output/test-korrekturrechnung.xml
index b71fafd..2507d5b 100644
--- a/office-alexander-logistics-app/src/test/resources/ksef/output/test-korrekturrechnung.xml
+++ b/office-alexander-logistics-app/src/test/resources/ksef/output/test-korrekturrechnung.xml
@@ -6,7 +6,7 @@
    <Naglowek>
       <KodFormularza kodSystemowy="FA (3)" wersjaSchemy="1-0E">FA</KodFormularza>
       <WariantFormularza>3</WariantFormularza>
-      <DataWytworzeniaFa>2026-05-14T09:50:45.565082350Z</DataWytworzeniaFa>
+      <DataWytworzeniaFa>2026-05-28T19:15:59.464195Z</DataWytworzeniaFa>
       <SystemInfo>Imixs eInvoice</SystemInfo>
    </Naglowek>
    <Podmiot1>
@@ -42,7 +42,7 @@
       <P_1>2025-02-10</P_1>
       <P_1M>Szczecin</P_1M>
       <P_2>FV/2025/001</P_2>
-      <P_6>2026-05-14</P_6>
+      <P_6>2026-05-28</P_6>
       <P_13_1>-900.00</P_13_1>
       <P_14_1>-207.00</P_14_1>
       <P_14_1W>-48.15</P_14_1W>