diff --git a/erpnext/accounts/doctype/sales_invoice/sales_invoice.json b/erpnext/accounts/doctype/sales_invoice/sales_invoice.json
index 9cfbd4f0053..f33576f6d9c 100644
--- a/erpnext/accounts/doctype/sales_invoice/sales_invoice.json
+++ b/erpnext/accounts/doctype/sales_invoice/sales_invoice.json
@@ -271,6 +271,7 @@
    "oldfieldtype": "Link",
    "options": "Customer",
    "print_hide": 1,
+   "reqd": 1,
    "search_index": 1
   },
   {
@@ -2330,7 +2331,7 @@
    "link_fieldname": "consolidated_invoice"
   }
  ],
- "modified": "2026-02-10 11:59:07.819903",
+ "modified": "2026-02-25 12:41:57.043459",
  "modified_by": "Administrator",
  "module": "Accounts",
  "name": "Sales Invoice",
diff --git a/erpnext/accounts/doctype/sales_invoice/sales_invoice.py b/erpnext/accounts/doctype/sales_invoice/sales_invoice.py
index b6261cc5707..d586d091707 100644
--- a/erpnext/accounts/doctype/sales_invoice/sales_invoice.py
+++ b/erpnext/accounts/doctype/sales_invoice/sales_invoice.py
@@ -119,7 +119,7 @@ class SalesInvoice(SellingController):
 		cost_center: DF.Link | None
 		coupon_code: DF.Link | None
 		currency: DF.Link
-		customer: DF.Link | None
+		customer: DF.Link
 		customer_address: DF.Link | None
 		customer_group: DF.Link | None
 		customer_name: DF.SmallText | None