All the  Buyers related information including the Tax details  is stored in Attendee/Buyer List.   Click the manage Icon for the Buyer whose tax details you want to  update.  On click of Manage Icon,  You will see a dropdown, select "Edit   Tax Details" options and you will see the information provided    by the Buyer. Make the necessary changes and save it.  Post this, ask the Buyer to click the  "Download  Invoice" button from the confirmation mail and  the buyer will get the updated invoice.  

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