I've got the information needed on handling Prepayment and overpayments in QuickBooks Online, jitendrakumar.

For Prepayments, you can use the Receive payment feature to record the advance payment made by your customer. 

First, ensure you have the customer listed on QuickBooks Online. Then, follow the steps I outlined below to record the Prepayment.

1. Click + New and select Receive payment.
2. Create a receive payment, then choose the customer using the dropdown arrow.
3. Under the Account column, select the invoice, then enter the amount of payment received
4. Select Save and New.

If not, you can follow the steps I provided below on how to add them:

1. Navigate to Sales and select Customers.
2. Click New customer.
3. In the Customer display name field, enter the display name for your customer (this is a required field).
4. Then, review each section and enter any other important customer info.
5. Tap Save.

On the other hand, you have three options on what to do when your customer overpays you, this includes:

• Applying the credit to an invoice.
• Refund the customer for the overpayment
• Enter the overpayment as a tip.

For the step-by-step guide, check this article: Handle a customer credit or overpayment in QuickBooks Online.

In addition, you can browse this link to learn how to receive and record invoice payments in QuickBooks Online: Record invoice payments in QuickBooks Online.

That should do it! If you have other questions about managing customer payments in QBO, kindly add them below. I'll be sure to assist.