feat: add outstanding field in payment schedule

erpnext/accounts/doctype/payment_schedule/payment_schedule.json

@@ -9,6 +9,7 @@
   "description",
   "discount_percentage",
   "discounted_amount",
+  "outstanding",
   "column_break_3",
   "due_date",
   "invoice_portion",
@@ -89,12 +90,18 @@
    "fieldtype": "Currency",
    "label": "Discounted Amount",
    "read_only": 1
+  },
+  {
+   "fieldname": "outstanding",
+   "fieldtype": "Currency",
+   "label": "Outstanding",
+   "read_only": 1
   }
  ],
  "index_web_pages_for_search": 1,
  "istable": 1,
  "links": [],
- "modified": "2021-02-08 12:45:25.734948",
+ "modified": "2021-02-09 20:47:56.617701",
  "modified_by": "Administrator",
  "module": "Accounts",
  "name": "Payment Schedule",

erpnext/patches.txt

@@ -757,3 +757,4 @@ erpnext.patches.v13_0.setup_fields_for_80g_certificate_and_donation
 erpnext.patches.v13_0.rename_membership_settings_to_non_profit_settings
 erpnext.patches.v12_0.create_taxable_value_field
 erpnext.patches.v12_0.add_company_link_to_einvoice_settings
+erpnext.patches.v13_0.update_payment_terms_outstanding

erpnext/patches/v13_0/update_payment_terms_outstanding.py

@@ -0,0 +1,15 @@
+# Copyright (c) 2020, Frappe Technologies Pvt. Ltd. and Contributors
+# MIT License. See license.txt
+
+from __future__ import unicode_literals
+import frappe
+
+def execute():
+	frappe.reload_doc("accounts", "doctype", "Payment Schedule")
+	if frappe.db.count('Payment Schedule'):
+		frappe.db.sql('''
+			UPDATE
+				`tabPayment Schedule` ps
+			SET
+				ps.outstanding = (ps.payment_amount - ps.paid_amount)
+		''')