How do I track a sale of product income to for a petty cash account.

You can use a Sales Receipt when your customer pays you instantly for goods or services in QuickBooks Online.

Since you've already set up your petty cash account in the Chart of Accounts, you need to associate it with your Sales Receipt so QuickBooks knows where the money is.

Follow the steps below:

1. Click the + Create button in the top-left corner.
2. Choose Sales Receipt, select a Customer.
3. In the Payment method dropdown, select Cash.
4. From the Deposit to dropdown, select your Petty Cash account.
5. In the Product/Service section, choose the product you sold.
6. Fill in the Qty, Rate, and Amount.
7. Then, click Save and Close.

Let me know if you have any other queries.