Quick answer
Open the submission in Feedback Studio, select the Download icon (bottom right) and then Digital Receipt.

Full answer
After submitting to Turntin, students should receive a copy of their submission receipt to their student email account within a couple of minutes. If not:

• Ask them to check their Junk/Spam folders.
• Ask them to go to the Turnitin assignment in Moodle and click “View Digital Receipt” next to the submission title.
• Go to the Turnitin assignment in Moodle and click on the title of the submission. With the submission open in Feedback Studio, click “Download” in the bottom right and select “Digital Receipt”. This will download a PDF version of the receipt to your computer.

This can provide evidence that your students have made a submission.