diff --git a/erpnext/manufacturing/doctype/job_card/job_card.js b/erpnext/manufacturing/doctype/job_card/job_card.js
index 52423c600d9..be8e534e1f0 100644
--- a/erpnext/manufacturing/doctype/job_card/job_card.js
+++ b/erpnext/manufacturing/doctype/job_card/job_card.js
@@ -355,6 +355,10 @@ frappe.ui.form.on("Job Card", {
 							default: frm.doc.for_quantity - frm.doc.total_completed_qty,
 						},
 						(data) => {
+							if (data.qty < 0) {
+								frappe.throw(__("Completed Quantity cannot be negative"));
+							}
+
 							frm.events.complete_job(frm, "Complete", data.qty);
 						},
 						__("Enter Value")
diff --git a/erpnext/manufacturing/doctype/job_card/job_card.py b/erpnext/manufacturing/doctype/job_card/job_card.py
index 16a454a984b..0807d98e61a 100644
--- a/erpnext/manufacturing/doctype/job_card/job_card.py
+++ b/erpnext/manufacturing/doctype/job_card/job_card.py
@@ -755,9 +755,10 @@ class JobCard(Document):
 
 	def set_process_loss(self):
 		precision = self.precision("total_completed_qty")
+		should_set_process_loss = self.total_completed_qty or self.process_loss_qty
 
 		self.process_loss_qty = 0.0
-		if self.total_completed_qty and self.for_quantity > self.total_completed_qty:
+		if should_set_process_loss and self.for_quantity > self.total_completed_qty:
 			self.process_loss_qty = flt(self.for_quantity, precision) - flt(
 				self.total_completed_qty, precision
 			)
diff --git a/erpnext/manufacturing/doctype/job_card/test_job_card.py b/erpnext/manufacturing/doctype/job_card/test_job_card.py
index ceb5ce299eb..f9b4cc0eabc 100644
--- a/erpnext/manufacturing/doctype/job_card/test_job_card.py
+++ b/erpnext/manufacturing/doctype/job_card/test_job_card.py
@@ -1157,6 +1157,19 @@ class TestJobCard(FrappeTestCase):
 
 		assert_operating_costs(s4, 3, [s, s3])
 
+	def test_set_process_loss(self):
+		nothing_done = frappe.new_doc("Job Card")
+		nothing_done.for_quantity = 10
+		nothing_done.total_completed_qty = 0
+		nothing_done.set_process_loss()
+		self.assertEqual(nothing_done.process_loss_qty, 0)
+
+		all_process_loss = frappe.new_doc("Job Card")
+		all_process_loss.for_quantity = 10
+		all_process_loss.process_loss_qty = 10
+		all_process_loss.set_process_loss()
+		self.assertEqual(all_process_loss.process_loss_qty, 10)
+
 
 def create_bom_with_multiple_operations():
 	"Create a BOM with multiple operations and Material Transfer against Job Card"