Global Records Rules (no group specified) are restrictive and block access

Group Record Rules limit access for the members of the group, but if there are multiple Record Rules then users are granted access from ALL the Record Rules (from all the groups they are in).

So if the first Record Rule grants a user access to all customers that can't be taken away by having another Record Rule that limits them to specific customers.  

You'd have to ensure that either:

• These users are not member of the group that is authorized to all customers

• OR change that Record Rule to be more restrictive and create another Record Rule that grants fuller access - and create a new group for the users that need the fuller access.

Hello Anu,

Actually i don't want to override the existing rule because each time when my custom module install at that time i don't know which module is already installed (base module) and because of which rule will not affect my rule that i don't know that's why. 

  Hi,

   Please try this https://stackoverflow.com/questions/53030606/inherit-and-replace-ir-rule-odoo-11