Emailing Invoice with Sales order Ref placeholder

Emailing Invoice with Sales order Ref placeholder

Hi Team, 

New to Zoho here and we are getting into the bits and bobs of Zoho. 

Would love to be able to add the sales order "placeholders" such as reference when emailing the invoice to customers. 

Our customers use their customers postal addresses as references and this reference is used in every situation throughout the sales order process. 

Attached photo below is my scenario.