One of my customers has a 5% rebate on all products they purchase from me, where do I put this in quickbooks?

Hello, @marianne-britten.

Thank you for posting in the Community. I'm here to help apply your 5% rebate to your customers.

You can apply a discount on your customer's invoice. If the discount field is not showing when creating the sales transaction, you'll have to turn this on to enable the feature.

Here's how:

1. Click the Gear icon on your QuickBooks account.
2. Under Your Company, click Account and Settings.
3. Go to the Sales tab on the left panel.
4. Click the Sales form content section to open it and check the tick box for Discount.
5. Click Save, and then Done.

When creating the invoice, you have the option to choose whether to apply it as discount percent or value. 

However, in QuickBooks Online you can only apply the discount on the whole transaction. If you need to discount each product line, you may refer to this related post for the workaround: https://quickbooks.intuit.com/community/Other-Questions/discounting-for-each-product-line/m-p/321478.

Additionally, you can refer to this article for some helpful details about setting up a discount for early payment: How to give your customers a discount for early payment.

Keep me posted if you have other questions about the process. I'm here to help however I can.