diff --git a/api/src/main/java/org/openmrs/module/billing/api/impl/BillServiceImpl.java b/api/src/main/java/org/openmrs/module/billing/api/impl/BillServiceImpl.java
index 5100c612..cc472b3c 100644
--- a/api/src/main/java/org/openmrs/module/billing/api/impl/BillServiceImpl.java
+++ b/api/src/main/java/org/openmrs/module/billing/api/impl/BillServiceImpl.java
@@ -22,8 +22,11 @@
 import java.net.URL;
 import java.security.AccessControlException;
 import java.text.DecimalFormat;
+import java.util.ArrayList;
 import java.util.Date;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 
 import com.itextpdf.io.font.constants.StandardFonts;
 import com.itextpdf.io.image.ImageDataFactory;
@@ -100,6 +103,58 @@ protected IEntityAuthorizationPrivileges getPrivileges() {
 	protected void validate(Bill bill) {
 	}
 	
+	private void mergeDuplicateLineItems(Bill bill) {
+		if (bill == null || bill.getLineItems() == null || bill.getLineItems().isEmpty()) {
+			return;
+		}
+		
+		List<BillLineItem> lineItems = bill.getLineItems();
+		List<BillLineItem> mergedItems = new ArrayList<>();
+		Map<String, BillLineItem> itemMap = new HashMap<>();
+		
+		for (BillLineItem item : lineItems) {
+			if (item == null) {
+				continue;
+			}
+			
+			String compositeKey = buildCompositeKey(item);
+			
+			if (itemMap.containsKey(compositeKey)) {
+				BillLineItem existingItem = itemMap.get(compositeKey);
+				int newQuantity = existingItem.getQuantity() + item.getQuantity();
+				existingItem.setQuantity(newQuantity);
+				
+				LOG.debug("Merged duplicate line item with key: " + compositeKey + ", new quantity: " + newQuantity);
+			} else {
+				itemMap.put(compositeKey, item);
+				mergedItems.add(item);
+			}
+		}
+		
+		bill.getLineItems().clear();
+		bill.getLineItems().addAll(mergedItems);
+	}
+	
+	private String buildCompositeKey(BillLineItem item) {
+		StringBuilder key = new StringBuilder();
+		
+		if (item.getBillableService() != null) {
+			key.append("service:").append(item.getBillableService().getUuid());
+		} else if (item.getItem() != null) {
+			key.append("stock:").append(item.getItem().getUuid());
+		}
+		
+		if (item.getItemPrice() != null) {
+			key.append("|price:").append(item.getItemPrice().getUuid());
+		}
+		
+		if (item.getPrice() != null) {
+			key.append("|amount:").append(item.getPrice().toPlainString());
+		}
+		
+		return key.toString();
+	}
+	
 	/**
 	 * Saves the bill to the database, creating a new bill or updating an existing one.
 	 *
@@ -117,6 +172,9 @@ public Bill save(Bill bill) {
 			throw new NullPointerException("The bill must be defined.");
 		}
 		
+		// Merge duplicate line items before any other processing
+		mergeDuplicateLineItems(bill);
+		
 		// Check for refund.
 		// A refund is given when the total of the bill's line items is negative.
 		if (bill.getTotal().compareTo(BigDecimal.ZERO) < 0 && !Context.hasPrivilege(PrivilegeConstants.REFUND_MONEY)) {
@@ -133,7 +191,6 @@ public Bill save(Bill bill) {
 				bill.setReceiptNumber(generator.generateNumber(bill));
 			}
 		}
-		// Check if there is an existing pending bill for the patient
 		List<Bill> bills = searchBill(bill.getPatient());
 		if (!bills.isEmpty()) {
 			Bill billToUpdate = bills.get(0);
@@ -143,18 +200,17 @@ public Bill save(Bill bill) {
 				billToUpdate.getLineItems().add(item);
 			}
 			
-			// Calculate the total payments made on the bill
+			mergeDuplicateLineItems(billToUpdate);
+			
 			BigDecimal totalPaid = billToUpdate.getPayments().stream().map(Payment::getAmountTendered)
 			        .reduce(BigDecimal.ZERO, BigDecimal::add);
 			
-			// Check if the bill is fully paid
 			if (totalPaid.compareTo(billToUpdate.getTotal()) >= 0) {
 				billToUpdate.setStatus(BillStatus.PAID);
 			} else {
 				billToUpdate.setStatus(BillStatus.PENDING);
 			}
 			
-			// Save the updated bill
 			return super.save(billToUpdate);
 		}
 		
@@ -228,10 +284,6 @@ public void apply(Criteria criteria) {
 		});
 	}
 	
-	/*
-	    These methods are overridden to ensure that any null line items (created as part of a bug in 1.7.0) are removed
-	    from the results before being returned to the caller.
-	 */
 	@Override
 	public List<Bill> getAll(boolean includeVoided, PagingInfo pagingInfo) {
 		List<Bill> results = super.getAll(includeVoided, pagingInfo);
@@ -267,8 +319,7 @@ public File downloadBillReceipt(Bill bill) {
 		        .concat(patient.getFamilyName() != null ? bill.getPatient().getFamilyName() : "").concat(" ")
 		        .concat(patient.getMiddleName() != null ? bill.getPatient().getMiddleName() : "");
 		String gender = patient.getGender() != null ? patient.getGender() : "";
-		String dob = patient.getBirthdate() != null
-		        ? Utils.getSimpleDateFormat("dd-MMM-yyyy").format(patient.getBirthdate())
+		String dob = patient.getBirthdate() != null ? Utils.getSimpleDateFormat("dd-MMM-yyyy").format(patient.getBirthdate())
 		        : "";
 		
 		File returnFile;
diff --git a/omod/src/main/resources/liquibase.xml b/omod/src/main/resources/liquibase.xml
index ca038697..f22dd3b3 100644
--- a/omod/src/main/resources/liquibase.xml
+++ b/omod/src/main/resources/liquibase.xml
@@ -869,6 +869,71 @@
 		</createIndex>
 	</changeSet>
 
+	<changeSet id="openmrs.billing-001-v3.0.0-20251110-01" author="Raj Prakash">
+		<preConditions onFail="MARK_RAN">
+			<not>
+				<indexExists indexName="unique_bill_line_item_idx"/>
+			</not>
+		</preConditions>
+		<comment>Add unique constraint to prevent duplicate line items with same service, price, and item price</comment>
+		
+		<!-- First, clean up any existing duplicates in the database -->
+		<sql>
+			CREATE TEMPORARY TABLE IF NOT EXISTS temp_duplicates AS
+			SELECT 
+				bill_id,
+				COALESCE(service_id, -1) as service_id_val,
+				COALESCE(item_id, -1) as item_id_val,
+				COALESCE(price_id, -1) as price_id_val,
+				price,
+				MIN(bill_line_item_id) as keep_id,
+				SUM(quantity) as total_quantity
+			FROM cashier_bill_line_item
+			WHERE voided = 0
+			GROUP BY bill_id, COALESCE(service_id, -1), COALESCE(item_id, -1), COALESCE(price_id, -1), price
+			HAVING COUNT(*) > 1;
+		</sql>
+		
+		<!-- Update quantities for the line items we're keeping -->
+		<sql>
+			UPDATE cashier_bill_line_item bli
+			INNER JOIN temp_duplicates td ON bli.bill_line_item_id = td.keep_id
+			SET bli.quantity = td.total_quantity;
+		</sql>
+		
+		<!-- Soft delete the duplicate line items (keep the first occurrence) -->
+		<sql>
+			UPDATE cashier_bill_line_item bli
+			INNER JOIN temp_duplicates td ON 
+				bli.bill_id = td.bill_id 
+				AND COALESCE(bli.service_id, -1) = td.service_id_val
+				AND COALESCE(bli.item_id, -1) = td.item_id_val
+				AND COALESCE(bli.price_id, -1) = td.price_id_val
+				AND bli.price = td.price
+				AND bli.bill_line_item_id != td.keep_id
+			SET bli.voided = 1,
+				bli.void_reason = 'Duplicate line item merged during database migration',
+				bli.date_voided = NOW(),
+				bli.voided_by = 1
+			WHERE bli.voided = 0;
+		</sql>
+		
+		<!-- Drop temporary table -->
+		<sql>
+			DROP TEMPORARY TABLE IF EXISTS temp_duplicates;
+		</sql>
+		
+		<!-- Create the unique index that handles NULL values properly -->
+		<createIndex indexName="unique_bill_line_item_idx" tableName="cashier_bill_line_item" unique="true">
+			<column name="bill_id"/>
+			<column name="service_id"/>
+			<column name="item_id"/>
+			<column name="price_id"/>
+			<column name="price"/>
+			<column name="voided"/>
+		</createIndex>
+	</changeSet>
+
 	<changeSet id="openmrs.billing-001-v3.0.0-20251007" author="Wikum Weerakutti">
 		<comment>Migrate global properties from 'cashier.*' prefix to 'billing.*'</comment>