diff --git a/erpnext/patches.txt b/erpnext/patches.txt
index df004ab..a03bd00 100644
--- a/erpnext/patches.txt
+++ b/erpnext/patches.txt
@@ -765,3 +765,4 @@
 erpnext.patches.v13_0.rename_discharge_date_in_ip_record
 erpnext.patches.v12_0.purchase_receipt_status
 erpnext.patches.v13_0.germany_make_custom_fields
+erpnext.patches.v13_0.germany_fill_debtor_creditor_number
diff --git a/erpnext/patches/v13_0/germany_fill_debtor_creditor_number.py b/erpnext/patches/v13_0/germany_fill_debtor_creditor_number.py
new file mode 100644
index 0000000..8482730
--- /dev/null
+++ b/erpnext/patches/v13_0/germany_fill_debtor_creditor_number.py
@@ -0,0 +1,31 @@
+# Copyright (c) 2019, Frappe and Contributors
+# License: GNU General Public License v3. See license.txt
+
+from __future__ import unicode_literals
+
+import frappe
+from erpnext.regional.germany.setup import make_custom_fields
+
+def execute():
+	"""Move account number into the new custom field debtor_creditor_number.
+
+	German companies used to use a dedicated payable/receivable account for
+	every party to mimick party accounts in the external accounting software
+	"DATEV". This is no longer necessary. The reference ID for DATEV will be
+	stored in a new custom field "debtor_creditor_number". 
+	"""
+	company_list = frappe.get_all('Company', filters={'country': 'Germany'})
+
+	for company in company_list:
+		party_account_list = frappe.get_all('Party Account', filters={'company': company.name}, fields=['name', 'account', 'debtor_creditor_number'])
+		for party_account in party_account_list:
+			if (not party_account.account) or party_account.debtor_creditor_number:
+				# account empty or debtor_creditor_number already filled
+				continue
+
+			account_number = frappe.db.get_value('Account', party_account.account, 'account_number')
+			if not account_number:
+				continue
+
+			frappe.db.set_value('Party Account', party_account.name, 'debtor_creditor_number', account_number)
+			frappe.db.set_value('Party Account', party_account.name, 'account', '')