Can quickbooks automatically generate receipt numbers mainting the number sequence for receipts from credit customers?

Yes, QuickBooks Online (QBO) automatically generates and maintains transaction numbers to help you keep track of your financial transactions, Kevin.

If, for any reason, the number isn't in sequence, you can toggle on the Custom transaction numbers feature in the Account and settings section of QBO. This feature allows you to alter or modify the transaction numbers, and the next time you create a receipt, QuickBooks will automatically sequence that. 

To turn on this feature, you need to follow these steps: 

1. Click the Gear icon and select Account and settings. 
2. Go to the Sales menu, and click the Sales form content section.
3. Click the Custom transaction numbers slider to enable it.
4. Hit Save and then Done.

Regarding your question of whether you can set up a password requirement if the receipt has to be altered once saved is not possible in QBO. However, you can still use the Custom transaction numbers feature to keep your transactions organized and easily searchable.

To learn more about this, check out this article: Add custom transaction numbers to sales forms in QuickBooks Online

Additionally, customizing your sales form contents is a breeze in QBO. For a detailed guide, please refer to this article: Customise invoices, estimates, and sales receipts in QuickBooks Online.

I'm just around the corner to help if you have any other concerns about managing sales transactions in QBO. Please don't hesitate to leave a comment below. Have a good day and stay safe.