Hi CR92,
Welcome to the Community. QuickBooks Online is a great program that gives you the ability to easily track sales and expenses. I'd be glad to help.
At this time, the option to export the mailing addresses for the last 400 clients isn't available. The program offers the possibility to print the packing slip for you customers. You can refer to this article to create and print a packing slip in QuickBooks Online.
If you'd like to include the option to export the mailing addresses for the last 400 clients in QuickBooks, I encourage you to send us Feedback by clicking on the Gear icon at the top. This is sent to our Development Team to consider for future updates.
Let me know if you have questions, I'll be happy to help.
