diff --git a/sync-service/src/main/java/com/teterialosjuanjos/tfg/sync_service/integration/dolibarr/DolibarrClient.java b/sync-service/src/main/java/com/teterialosjuanjos/tfg/sync_service/integration/dolibarr/DolibarrClient.java
index 1d55fc4..a450009 100644
--- a/sync-service/src/main/java/com/teterialosjuanjos/tfg/sync_service/integration/dolibarr/DolibarrClient.java
+++ b/sync-service/src/main/java/com/teterialosjuanjos/tfg/sync_service/integration/dolibarr/DolibarrClient.java
@@ -9,7 +9,6 @@ import org.springframework.stereotype.Component;
 import org.springframework.web.client.RestClient;
 
 import java.util.List;
-import java.util.Map;
 
 /**
  * Typed HTTP client for the Dolibarr REST API.
@@ -182,17 +181,38 @@ public class DolibarrClient {
     // ── Invoices ─────────────────────────────────────────────────────────
 
     /**
-     * Creates an invoice linked to an existing order.
+     * Creates an invoice linked to an existing Dolibarr order, copying its lines.
      *
-     * @param orderId Dolibarr internal order ID
-     * @param socid   customer (thirdparty) internal ID — required by Dolibarr even with fk_commande
+     * <p>Dolibarr's {@code POST /invoices} does not copy order lines automatically when
+     * only {@code fk_commande + socid} are sent — lines must be included in the body.</p>
+     *
+     * @param order the created order (must have {@code id}, {@code socid}, and {@code lines})
      */
-    public DolibarrInvoiceDto createInvoiceFromOrder(Integer orderId, Integer socid) {
-        log.debug("Creating Dolibarr invoice from orderId={}", orderId);
-        Map<String, Object> body = Map.of("fk_commande", orderId, "socid", socid);
+    public DolibarrInvoiceDto createInvoiceFromOrder(DolibarrOrderDto order) {
+        log.debug("Creating Dolibarr invoice from orderId={}", order.id());
+
+        List<DolibarrInvoiceDto.InvoiceLine> invoiceLines = order.lines() == null
+                ? List.of()
+                : order.lines().stream()
+                        .map(l -> DolibarrInvoiceDto.InvoiceLine.builder()
+                                .fkProduct(l.fkProduct())
+                                .productRef(l.productRef())
+                                .desc(l.desc())
+                                .subprice(l.subprice())
+                                .qty(l.qty())
+                                .tvaTx(l.tvaTx())
+                                .build())
+                        .toList();
+
+        DolibarrInvoiceDto invoiceBody = DolibarrInvoiceDto.builder()
+                .fkCommande(order.id())
+                .socid(order.socid())
+                .lines(invoiceLines)
+                .build();
+
         Integer newId = restClient.post()
                 .uri("/invoices")
-                .body(body)
+                .body(invoiceBody)
                 .retrieve()
                 .body(Integer.class);
 
diff --git a/sync-service/src/main/java/com/teterialosjuanjos/tfg/sync_service/integration/dolibarr/dto/DolibarrInvoiceDto.java b/sync-service/src/main/java/com/teterialosjuanjos/tfg/sync_service/integration/dolibarr/dto/DolibarrInvoiceDto.java
index c37b3b1..9a04475 100644
--- a/sync-service/src/main/java/com/teterialosjuanjos/tfg/sync_service/integration/dolibarr/dto/DolibarrInvoiceDto.java
+++ b/sync-service/src/main/java/com/teterialosjuanjos/tfg/sync_service/integration/dolibarr/dto/DolibarrInvoiceDto.java
@@ -3,18 +3,41 @@ package com.teterialosjuanjos.tfg.sync_service.integration.dolibarr.dto;
 import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
+import lombok.Builder;
+
+import java.util.List;
 
 /**
- * Minimal representation of a Dolibarr invoice.
- * Used for {@code GET /invoices/{id}} responses after creation via {@code POST /invoices}.
+ * Represents a Dolibarr invoice.
+ * Used for {@code POST /invoices} request bodies (with lines) and {@code GET /invoices/{id}} responses.
  */
+@Builder
 @JsonIgnoreProperties(ignoreUnknown = true)
 @JsonInclude(JsonInclude.Include.NON_NULL)
 public record DolibarrInvoiceDto(
         Integer id,
         String ref,
+        Integer socid,
         /** Linked order internal ID */
         @JsonProperty("fk_commande") Integer fkCommande,
         /** 0 = draft, 1 = validated, 2 = paid, 3 = abandoned */
-        Integer statut
-) {}
+        Integer statut,
+        List<InvoiceLine> lines
+) {
+
+    /**
+     * One line of an invoice. Mirrors {@link DolibarrOrderDto.OrderLine} fields
+     * so order lines can be copied directly into the invoice on creation.
+     */
+    @Builder
+    @JsonIgnoreProperties(ignoreUnknown = true)
+    @JsonInclude(JsonInclude.Include.NON_NULL)
+    public record InvoiceLine(
+            @JsonProperty("fk_product") Integer fkProduct,
+            @JsonProperty("product_ref") String productRef,
+            String desc,
+            Double subprice,
+            Double qty,
+            @JsonProperty("tva_tx") Double tvaTx
+    ) {}
+}
diff --git a/sync-service/src/main/java/com/teterialosjuanjos/tfg/sync_service/sync/OrderSyncService.java b/sync-service/src/main/java/com/teterialosjuanjos/tfg/sync_service/sync/OrderSyncService.java
index b5128ff..6496503 100644
--- a/sync-service/src/main/java/com/teterialosjuanjos/tfg/sync_service/sync/OrderSyncService.java
+++ b/sync-service/src/main/java/com/teterialosjuanjos/tfg/sync_service/sync/OrderSyncService.java
@@ -130,9 +130,8 @@ public class OrderSyncService {
 
         DolibarrOrderDto createdOrder = dolibarrClient.createOrder(orderDto);
 
-        // 3. Create linked invoice
-        DolibarrInvoiceDto invoice = dolibarrClient.createInvoiceFromOrder(
-                createdOrder.id(), customer.id());
+        // 3. Create linked invoice with lines copied from the order
+        DolibarrInvoiceDto invoice = dolibarrClient.createInvoiceFromOrder(createdOrder);
 
         // 4. Persist mapping to prevent re-import
         orderMappingRepository.save(OrderMapping.builder()