An attachment or reference file, such as a picture of the bill receipt, can be associated with your bills in Zoho Books. This can be done while creating a new bill or editing an existing bill.
Scroll down to find the option Attach Reference File and click on Upload File to select and attach the required file.
You can also attach a file using the paperclip icon prensent at the top of the bill preview.
Note : The maximum file allowed is 5 MB.