diff --git a/Model-Design-Guidelines.md b/Model-Design-Guidelines.md
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--- a/Model-Design-Guidelines.md
+++ b/Model-Design-Guidelines.md
@@ -1,3 +1,9 @@
+### Numbering Series
+
+For auto naming, use the format `[MOD]-[DOC]-.YYYY.-` where MOD is the module abbreviation and DOC is the DocType abbrevation.
+
+For example: Lead in CRM module should be `CRM-LEAD-.YYYY.-`
+
 ### Avoid hard coding of Roles
 
 No business logic should be based on hard coded roles. Either make it a configuration or set a property in User / Employee whether user has the permission to do the action.