Why are they reviewing an invoice payment?

Welcome to the Community! I've got some information as to why QuickBooks is reviewing an invoice payment. 

At QuickBooks, reviewing your invoice payments is conducted to ensure the enhancement of the overall security and reliability of the financial records. Know that if payments are taking longer than usual, they may not be on hold. For new QuickBooks Payments users, the first few payments take longer to process while QuickBooks sets everything up. 

You can refer to these guides to learn more about how long it takes to get customer payments into your bank account and learn more about funds : 

• Find out when QuickBooks Payments deposits customer payments. 
• Why are my funds on hold?

In addition, you can record invoice payments when a customer pays an invoice to balance your accounts. 

You're always welcome to reply whenever you have further questions regarding invoice payments or anything related to QuickBooks. I'm here to help you. Stay safe.