Is there a way to allow customers to log into my QB online license and view their transaction history... and at the same time make payments?

It's my pleasure to share with you an insight about letting your customer view their transactions in your QuickBooks account, Iceguy.

In QuickBooks, you have the options for user roles and access permissions. Here are the steps below to acheive it.

To add a new user:

1. Select Settings menu, then select Manage users.
2. Select Add user, then select a user type. 
3. Click Next, then select the access rights for the user. 
4. Select Next, then select the user settings, if applicable. Then, select Next.
5. Enter the user’s name and email address. Then click Save.

Once done, your new users receive an invite to join the company. Ask them to select the link in the email to create a new Intuit Account, or just sign in if they have an existing one.

You can also manage user role or permissions by following the steps below:

1. Select Settings menu.
2. Select Manage users.
3. Find the user you want to edit. Then select Edit in the Action column.

• You can change the User type ▼.
• Select the user settings you want to manage (if applicable).

Concerning making payments, they can pay bills, write and print checks, and view checks reports, or make bills and purchases billable to customers. 

Should you need to let your customer pay you online, visit this article to learn more about this process: Take and process payments in QuickBooks Online.

Get back here and post some more if you have additional concerns. I'll be there right away to guide you again. 

@Iceguy 

Who are these "customers"? Are you helping them to book their QBO account? or are you actually sending them your invoice and you are thinking of letting them check their own bill?