Our customers close view invoice and then it’s shows the invoice is unavailable. Is anyone else experiencing this issue?

Nice to have you in the Community space, @guernseypartypri.

I've created an invoice in my QBSE test account to replicate this situation and didn't bump into this issue you mentioned. To help fix this, have your customers access their accounts through a private browser. It's a great way of isolating the issue since it doesn’t store data in the cache. 

Here are the following keyboard shortcuts: 

• Google Chrome: Ctrl + Shift + N
• Microsoft Edge: Ctrl + Shift + P
• Firefox: Ctrl + Shift + P
• Safari: Command + Shift + N

From there, let them view the invoice again and verify if it's showing. If it works, go back to their regular browser and clear its cache. This deletes the stored cache files and gets a clean slate in the browser. They, can also use other supported browsers. 

Once you receive the payments from your customers, you can click the Mark as paid links in the Action column. You can also continue to take other actions, like printing or exporting them as PDFs. 

To learn more about invoicing in your QBSE account, check out this article: Create invoices in QuickBooks Self-Employed.

Aside from invoices, you can also categorise your income and expenses to put them to the correct line of your Schedule C categories. To know more, you can check out this link: Categorise transactions in QuickBooks Self-Employed.

In case you have other concerns or questions about invoices or managing your QBSE account, tag me in your reply. I’ll be around to answer them. Have a great week!