How do i deal with a sales invoice with a negative value, i sold a car and took part ex in at more value than car sold, quickbooks wont let me do an invoice this way

Handling a sales invoice with a negative value in QuickBooks Online (QBO) can be tricky, jwsprestige.

QuickBooks allows you to enter negative amounts. However, it shouldn't have a negative total or balance due. Otherwise, it won't let you save your transaction.

Instead of creating a negative invoice, we can create a credit note for the amount that exceeds the value of the car sold. This will adjust the customer’s account balance accordingly. Here are a few steps you can take to manage this situation:
 

1. Open your QBO account.
2. Select + New, then choose Credit note.
3. From the Customer dropdown, select the customer's name.
4. Enter the credit note details, such as the date and the amount.
5. When you're done, click Save and close.

Once done, you can then apply this credit memo to future invoices for the same customer. Here's how:

1. Select + New, then Receive payment.
2. From the Customer dropdown, select the customer.
3. In the Outstanding Transactions section, select the open invoice you want to apply the credit note to.
4. In the Credits section, select the one you created.
5. For the open invoice in the Payment column, enter how much of the credit you want to apply.
6. Leave the Payment method, Reference no, Deposit to, and Amount received fields blank.
7. Fill out the rest of the form, including the Payment date.
8. When you're done, click Save and close.

You'll want to visit this article on how to handle overpayments in QuickBooks: Handle a customer credit or overpayment in QuickBooks Online.

Keep in touch if you have more questions regarding your invoices and handling payments, or if there's something else we can do for you. We'd be glad to provide the help you need.