How can I receive or download all the Intuit subscription Invoices for last 6 years?

We're glad to have you here, @afriscan-int-ltd.

I want to make sure you can download the subscription history in QuickBooks Online. 

QuickBooks Subscription invoices are sent via email every month to the primary contact listed in your Settings. It would be my pleasure to walk you through the steps on how to get a copy for subscription in your account. Please take note that the billing history will display only the last six (6) months'. 

Here's how:

1. Click on the Gear icon.
2. Select Account and Settings.
3. Choose the Billing & Subscription tab. 
4. In the QuickBooks section, click on View payment history. 

     5. On the Payment History page, select a date range and then click on the printer icon to print.

For the detailed guide, check out this article: View your QuickBooks Online payment history.

To get the six years subscription, I suggest contacting our Customer Care Team. They have tools to access your whole subscription history and check why you're not receiving any monthly receipts. They are open Monday-Friday 6:00 AM - 6:00 PM and Saturday 6:00 AM - 3:00 PM Pacific Time.

Let me guide you how:

1. Go to the Help menu and click Contact Us. 
2. Enter your concern in the description field, then hit Let's talk. 
3. Choose either Start messaging or Get a callback. 
4. Complete the needed information to accomplish the process. 

Please check out this article: Update your billing and subscription info in QuickBooks Online. This link guides you on how to update payment and personal information in QBO. Also, you'll learn more about how to change the billing cycle.

Let me know if you have other questions. I'm always here to help. Take good care.