How to get rid of the decimal point in payment? Lets say my payment is 124.10 but my invoice is $124.12

Welcome to the Community, @userhuini.

Since this is an underpayment, you can go ahead and write off this specific amount to get rid of that decimal point. To do this, you need to create a Journal Entry (JE).

Before doing so, I suggest consulting your accountant for further assistance with the process to ensure your books are accurate.

Here's how:

1. In QuickBooks Online (QBO), go to the + New option at the top left to create a JE. 
2. Enter the Journal Date (end of the time period).
3. On the first line, select the account affected by the invoice from the in the Account column.
4. In the Debit column, enter the amount.
5. In the second line, pick Accounts Receivable from the Accounts drop-down. The amount should be automatically entered in the Credits column.
6. Choose the customer from the drop-down list in the Name field.
7. Hit Save and close to complete.

If you want to learn more about writing off customers' or vendors' balance, check out this article: Resolve A/R or A/P balances on a cash basis Balance Sheet.

Reach out to me in the comment section below if you have any other questions or concerns. I'll be here to help. Have a wonderful day!