Hi VR7, 

Thanks for joining us on this thread. 

The invoice no. field on the Estimates by Customer reports is designed to only contain one invoice number, and so we've found this will not populate for users who have progress invoicing enabled (where you can create multiple partial invoices from a single estimate).

If you don't use progress invoicing, you can disable this feature so that the report will populate with the invoice no. To do this, go to the Cogwheel > Account & settings > Sales > Progress invoicing > Slide to off. Any invoices raised from estimates after this point will then display the number in the report.

Please get back to us below if you have any questions! :smiling_face_with_smiling_eyes: