How can I find the receipt for my MacBookPro?

Hi,

Following step by step instruction could solve your issue.

1. Go to ReportaProblem.apple.com from your favorite browser on your MAC or Windows PC.
2. Login using your registered Apple email ID and password.
3. In the scroll down list find the order you want a receipt for.
4. Select the order you want the receipt and then click on “View Invoice”

Did you buy direclty from Apple? kaz-k's steps work well, but not if you bought from a reseller.

First check ALL your email accounts. Apple sends an email, typically to the email address that is your Apple ID. The link to the invoice can, however, be frustratingly small. Example:

Also, the invoices appears available that way for only about 18 months. If the purchase was older, you can try calling Apple support.