diff --git a/library/src/main/java/org/mustangproject/ZUGFeRD/ZUGFeRD2PullProvider.java b/library/src/main/java/org/mustangproject/ZUGFeRD/ZUGFeRD2PullProvider.java
index 02f59b5c..ad87e52f 100644
--- a/library/src/main/java/org/mustangproject/ZUGFeRD/ZUGFeRD2PullProvider.java
+++ b/library/src/main/java/org/mustangproject/ZUGFeRD/ZUGFeRD2PullProvider.java
@@ -306,7 +306,8 @@ public class ZUGFeRD2PullProvider implements IXMLProvider {
 		String chargeIndicator = "false";
 		if ((allowance.getPercent() != null) && (profile == Profiles.getByName("Extended"))) {
 			percentage = "<ram:CalculationPercent>" + vatFormat(allowance.getPercent()) + "</ram:CalculationPercent>";
-			percentage += "<ram:BasisAmount>" + currencyFormat(item.getValue()) + "</ram:BasisAmount>";
+			// BT-137/BT-142: BasisAmount = the value the percentage is applied to = line subtotal (price/basisQty)*qty
+			percentage += "<ram:BasisAmount>" + currencyFormat(item.getValue().multiply(item.getQuantity())) + "</ram:BasisAmount>";
 		}
 		if (allowance.isCharge()) {
 			chargeIndicator = "true";
diff --git a/library/src/test/java/org/mustangproject/ZUGFeRD/CalculationTest.java b/library/src/test/java/org/mustangproject/ZUGFeRD/CalculationTest.java
index d902e6c3..535aa862 100644
--- a/library/src/test/java/org/mustangproject/ZUGFeRD/CalculationTest.java
+++ b/library/src/test/java/org/mustangproject/ZUGFeRD/CalculationTest.java
@@ -559,6 +559,92 @@ public class CalculationTest extends ResourceCase {
 		assertEquals(new BigDecimal("55.00"), lc.getItemTotalNetAmount());
 	}
 
+	@Test
+	public void testLineLevelAllowanceBasisAmountIsLineSubtotal() {
+		// BT-137: line-allowance BasisAmount = (price / basisQty) * qty (line subtotal), NOT the per-unit value.
+		// price=128.49 per 100 LTR, qty=50 LTR, basisQty=100
+		// line subtotal before allowance = 128.49 / 100 * 50 = 64.245 -> 64.25 (HALF_UP, BR-DEC-25)
+		// allowance ActualAmount = 10% of 64.245 = 6.4245 -> 6.42
+		SimpleDateFormat sqlDate = new SimpleDateFormat("yyyy-MM-dd");
+
+		Invoice invoice = new Invoice();
+		invoice.setDocumentName("Rechnung");
+		invoice.setNumber("BT137-ALLOWANCE");
+		try {
+			invoice.setIssueDate(sqlDate.parse("2024-01-01"));
+			invoice.setDueDate(sqlDate.parse("2024-01-31"));
+		} catch (Exception e) {
+			LOGGER.error("Failed to set dates", e);
+		}
+		TradeParty sender = new TradeParty("Sender GmbH", "Hauptstr. 1", "10115", "Berlin", "DE");
+		sender.addVATID("DE123456789");
+		invoice.setSender(sender);
+		TradeParty recipient = new TradeParty("Recipient GmbH", "Nebenstr. 2", "10116", "Berlin", "DE");
+		recipient.addVATID("DE987654321");
+		invoice.setRecipient(recipient);
+
+		Product product = new Product("Testartikel", "", "LTR", BigDecimal.ZERO);
+		Item item = new Item(product, new BigDecimal("128.49"), new BigDecimal("50"));
+		item.setBasisQuantity(new BigDecimal("100"));
+		item.addAllowance(new Allowance().setPercent(new BigDecimal(10)).setTaxPercent(BigDecimal.ZERO));
+		invoice.addItem(item);
+
+		ZUGFeRD2PullProvider zf2p = new ZUGFeRD2PullProvider();
+		zf2p.setProfile(Profiles.getByName("Extended"));
+		zf2p.generateXML(invoice);
+
+		String theXML = new String(zf2p.getXML(), StandardCharsets.UTF_8);
+		assertThat(theXML).valueByXPath("//*[local-name()='SpecifiedTradeAllowanceCharge'][*[local-name()='ChargeIndicator']/*[local-name()='Indicator']='false']/*[local-name()='BasisAmount']")
+			.asString()
+			.isEqualTo("64.25"); // (128.49/100)*50 = 64.245 rounded HALF_UP
+		assertThat(theXML).valueByXPath("//*[local-name()='SpecifiedTradeAllowanceCharge'][*[local-name()='ChargeIndicator']/*[local-name()='Indicator']='false']/*[local-name()='ActualAmount']")
+			.asString()
+			.isEqualTo("6.42"); // 64.245 * 0.10 = 6.4245 rounded HALF_UP
+	}
+
+	@Test
+	public void testLineLevelChargeBasisAmountIsLineSubtotal() {
+		// BT-142: line-charge BasisAmount = (price / basisQty) * qty (line subtotal), NOT the per-unit value.
+		// price=200.00 per 4 units, qty=10, basisQty=4
+		// line subtotal before charge = 200.00 / 4 * 10 = 500.00
+		// charge ActualAmount = 5% of 500.00 = 25.00
+		SimpleDateFormat sqlDate = new SimpleDateFormat("yyyy-MM-dd");
+
+		Invoice invoice = new Invoice();
+		invoice.setDocumentName("Rechnung");
+		invoice.setNumber("BT142-CHARGE");
+		try {
+			invoice.setIssueDate(sqlDate.parse("2024-01-01"));
+			invoice.setDueDate(sqlDate.parse("2024-01-31"));
+		} catch (Exception e) {
+			LOGGER.error("Failed to set dates", e);
+		}
+		TradeParty sender = new TradeParty("Sender GmbH", "Hauptstr. 1", "10115", "Berlin", "DE");
+		sender.addVATID("DE123456789");
+		invoice.setSender(sender);
+		TradeParty recipient = new TradeParty("Recipient GmbH", "Nebenstr. 2", "10116", "Berlin", "DE");
+		recipient.addVATID("DE987654321");
+		invoice.setRecipient(recipient);
+
+		Product product = new Product("Testartikel", "", "H87", BigDecimal.ZERO);
+		Item item = new Item(product, new BigDecimal("200.00"), new BigDecimal("10"));
+		item.setBasisQuantity(new BigDecimal("4"));
+		item.addCharge(new Charge().setPercent(new BigDecimal(5)).setTaxPercent(BigDecimal.ZERO));
+		invoice.addItem(item);
+
+		ZUGFeRD2PullProvider zf2p = new ZUGFeRD2PullProvider();
+		zf2p.setProfile(Profiles.getByName("Extended"));
+		zf2p.generateXML(invoice);
+
+		String theXML = new String(zf2p.getXML(), StandardCharsets.UTF_8);
+		assertThat(theXML).valueByXPath("//*[local-name()='SpecifiedTradeAllowanceCharge'][*[local-name()='ChargeIndicator']/*[local-name()='Indicator']='true']/*[local-name()='BasisAmount']")
+			.asString()
+			.isEqualTo("500.00"); // (200.00/4)*10 = 500.00
+		assertThat(theXML).valueByXPath("//*[local-name()='SpecifiedTradeAllowanceCharge'][*[local-name()='ChargeIndicator']/*[local-name()='Indicator']='true']/*[local-name()='ActualAmount']")
+			.asString()
+			.isEqualTo("25.00"); // 500.00 * 0.05 = 25.00
+	}
+
 	/**
 	 * LineCalculator should not throw an exception when calculating a non-terminating decimal expansion
 	 */