In QBO, it’s mainly because of unapplied transactions like credit memos, journal entries, and payments not properly applied against the open invoice. In other words, it’s one more step to be done in QBO.
Follow the following steps:
Step1: Go to the Create “+” plus sign and top corner and select Receive Payment.
Step 2: Select Customer. QuickBooks will show both open invoice and unapplied credit transaction.
Step 3: Next, apply the invoice to the unapplied transaction.
Step 4: Be sure to review it. The amount of the transaction on Receive Payment screen should be zero.
Step 4: Click Save and Close.
In the Customer Center, the invoice should show as paid. Also, should fix the A/R Aging.