I am wondering if the clients decide to stop using QBO in future, can he/she download all invoices attachment in the system other than financial figure and lists?

Hi there,

Glad to learn you and your clients are using QuickBooks to streamline your work. I'd be happy to share more information about downloading all invoice attachments. 

QuickBooks is a powerful program which offers cutting-edge features which help with managing your business. To download all attachments on the account, follow the steps below: 

1.     Go to the  Gear icon ⚙️.
2.     Under Lists, choose All Lists.
3.     Select Attachments.

For more information on this, I recommend the following article: Attachments in QuickBooks Online.

Give this a try and if you have questions, I recommend contacting our support team using this link. Otherwise, feel free to leave a comment below. I'll be on standby.