diff --git a/addons/purchase/models/purchase.py b/addons/purchase/models/purchase.py
index a05edfedbf1..ffb917359d7 100644
--- a/addons/purchase/models/purchase.py
+++ b/addons/purchase/models/purchase.py
@@ -563,21 +563,20 @@ class PurchaseOrderLine(models.Model):
             else:
                 line.qty_received_manual = 0.0
 
-    @api.model
-    def create(self, values):
-        if values.get('display_type', self.default_get(['display_type'])['display_type']):
-            values.update(product_id=False, price_unit=0, product_uom_qty=0, product_uom=False, date_planned=False)
+    @api.model_create_multi
+    def create(self, vals_list):
+        for values in vals_list:
+            if values.get('display_type', self.default_get(['display_type'])['display_type']):
+                values.update(product_id=False, price_unit=0, product_uom_qty=0, product_uom=False, date_planned=False)
+            else:
+                values.update(self._prepare_add_missing_fields(values))
 
-        order_id = values.get('order_id')
-        if 'date_planned' not in values:
-            order = self.env['purchase.order'].browse(order_id)
-            if order.date_planned:
-                values['date_planned'] = order.date_planned
-        line = super(PurchaseOrderLine, self).create(values)
-        if line.order_id.state == 'purchase':
-            msg = _("Extra line with %s ") % (line.product_id.display_name,)
-            line.order_id.message_post(body=msg)
-        return line
+        lines = super().create(vals_list)
+        for line in lines:
+            if line.product_id and line.order_id.state == 'purchase':
+                msg = _("Extra line with %s ") % (line.product_id.display_name,)
+                line.order_id.message_post(body=msg)
+        return lines
 
     def write(self, values):
         if 'display_type' in values and self.filtered(lambda line: line.display_type != values.get('display_type')):
@@ -756,6 +755,19 @@ class PurchaseOrderLine(models.Model):
             'display_type': self.display_type,
         }
 
+    @api.model
+    def _prepare_add_missing_fields(self, values):
+        """ Deduce missing required fields from the onchange """
+        res = {}
+        onchange_fields = ['name', 'price_unit', 'product_qty', 'product_uom', 'taxes_id', 'date_planned']
+        if values.get('order_id') and values.get('product_id') and any(f not in values for f in onchange_fields):
+            line = self.new(values)
+            line.onchange_product_id()
+            for field in onchange_fields:
+                if field not in values:
+                    res[field] = line._fields[field].convert_to_write(line[field], line)
+        return res
+
     @api.model
     def _prepare_purchase_order_line(self, product_id, product_qty, product_uom, company_id, supplier, po):
         partner = supplier.name