Hi simon82,
Thanks for posting in the Community! You can add Schedule of Payments to your customer's invoice by adding it to the Message on invoice text box or if your Schedule of Payments is in a PDF file, you can add it as an attachment. Here's how:
For your reference, you can also check this article: Add or delete attachments in QuickBooks Online.
Feel free to post again if you have any other questions, we're here to help. Have a nice day!
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