Merge pull request #6971 from ShraddhaRanjane/patch-2

Update naming-series.md
diff --git a/erpnext/docs/user/manual/en/setting-up/settings/naming-series.md b/erpnext/docs/user/manual/en/setting-up/settings/naming-series.md
index df7de6d..086a272 100644
--- a/erpnext/docs/user/manual/en/setting-up/settings/naming-series.md
+++ b/erpnext/docs/user/manual/en/setting-up/settings/naming-series.md
@@ -46,3 +46,12 @@
 
 {next}
 
+### 4. Custom Field in Naming Series
+ Some companies prefers to make use of "short-codes" for suppliers, i.e. WN for company "Web Notes" that later can be used in naming series for quick identification.
+ 
+#### Example:
+
+    A custom field "Vendor ID" is created under Document: Supplier.
+    Then under Naming Series, we should allow something like
+        PO-.YY.MM.-.vendor_id.-.#####
+        Resulting in "PO-1503-WN-00001"