You can if you've enabled SmugMug's Proof-Delay feature.
When a customer orders, we'll email you to let you know. You can check the order by going to your Account Settings > Business > Selling and clicking Manage. The most recent order will appear at the top of the list. Click on Order Details to verify that the crops are good.
Once you've checked everything, or adjusted the crop as needed, click Send to the Lab Now to send your customer's order to print.