Hello there, Fernando.

I'm here to help you in recording those transactions.

You're already on the right track with entering the rebates. You only need a few more steps to complete the process. After the vendor sends you a refund for a bill that is already paid, you'll need to record it as a deposit in QuickBooks. Here's how:

1. Go to the Banking menu, then select Make Deposits.
2. If the Payments to Deposit window appears, click OK.
3. In the Make Deposits window, click the Received from drop-down menu and then choose the supplier who sent you the refund.
4. In the From Account drop-down menu, select the appropriate accounts payable account.
5. In the Amount column, enter the actual amount of the refund.
6. Enter a memo, cheque number, payment method, and class as needed.
7. Hit Save & Close.

After that, you'll have to record a bill credit for the refunded amount:
 

1. Go to the Vendors menu, then select Enter Bills.
2. Tick the Credit radio button to account for the return of goods.
3. Enter the vendor name and the other necessary information.
4. Select the Expenses tab and then enter the accounts on the original bill. If this for the returned items, select the Items Tab, then enter the returned parts.
5. In the Amount column, enter the appropriate amount for each account/item.
6. Click Save and Close.

Once done, you can now link the deposit to the bill credit:

1. Go to the Vendors menu, then select Pay Bills.
2. Check the deposit that matches the vendor check amount.
3. Select Set Credits, then apply the bill credit you created earlier.
4. Hit Done, then select Pay Selected Bills.
5. Click Done again.

To learn more about this process, you can visit this link: Record a vendor refund. 

With regard to the customer rebate, you can just create a credit memo or issue a refund check to record the returned transactions. In addition, here's an article that you can read to learn how to refund a credit card payment in QuickBooks Desktop: Void or refund customer payments.

Do you have any other questions in mind? Feel free to leave them below and I'll get back to you as soon as I can.