Can you help me to solve the matter for the default to discount value. Or just only do adjust manually every time we record the receipt.

Great to have you here. It's my priority to help you apply a discount value on your receipt, patihah.

In QuickBooks Online (QBO), we can apply the discount to the total amount of your sales receipt as a Discount percentage (enter the discount as a percentage) or Discount value (enter a specific amount) in the discount field. Let's make sure we enable the Discount feature in the Account and Settings page. Let me show you how: 

1. Go to the Gear icon on the top menu. 
2. Select Account and Settings.
3. Tick the Sales tab. 
4. In the Sales form content section, tap the Pencil ✏ icon. 
5. Turn on the Discount option.
6. Press Save and Done.

Then, apply the discount to your sales receipt. Just follow the steps and details in this article: Add a discount to an invoice or sales receipt in QuickBooks Online. Then, go to Step 2: Apply a discount section.

If you need to create a discount item with a fixed price, follow the steps below:

1. Go to the Gear icon on the top menu and choose Products and Services.
2. Click New and select Non-inventory or Service for the type.
3. Enter the name of the discount in the Name field. 
4. Select a category. This should be the item you are selling and giving a discount.
5. In the Sales price/rate field, enter the discount as a negative amount.
6. From the Income account drop-down menu, tap the Discount given account.
7. From the Sales tax category drop-down menu, select Nontaxable.
8. Press Save and close. 

This will set a discount for the amount that you can add after each item. Then, record the payment once you receive the payment from the customer.

Visit our Managing Customers and Income page for more insights about managing your customers' transactions.

You can always count on me if you need a hand with categorizing your transactions or any QBO related. Assistance is just one click away. Have a great day.