Thanks for following the thread, @tkphua. With your concern, you can specifically create an estimate as a DO before generating an invoice.

Before that, you'll have to create a new customised estimate and name the form as DO.

Let me show you how:

1. Click the Gear icon on the top right and then select Custom form styles.
2. Hit New and then choose Estimate.
3. Go to the Content tab and then select the Pencil icon on the Header part.
   
4. From the Form section, change the Form name to DO.
   
5. Make necessary customisations.
6. Hit Done.

Once done, you can use this new form style by assigning it as a default estimate form for estimates.

From the Custom form styles window, find the newly created estimate form and then click the drop-down arrow and then choose to Make default.

You can now create an estimate. Just a heads up, make sure to uncheck the tax column on the estimate window to avoid showing the tax amount. Also, we're unable to remove the Total (amount) since this is a default element of an invoice. It would be great if we're able to offset it to boost your QBO experience.

1. Click + New, select Estimate.
2. Choose a customer from the Customer drop-down.
3. Set the  Estimate Date and the Expiration Date.
4. Enter the products and services you plan to sell.
5. Enter any other info you need and then uncheck the Tax column boxes.
   
6. When you're ready, select Save and send to send it directly.

It will look like this when you send the form.

When it's time to generate the bill for the customer, you can select +New on the upper left and then select Invoice. Select the customer's name to see open estimate/DO. From the right frame, click Add to choose the correct estimate transaction. Then hit Copy to invoice. Ensure to Save and send/Save and close the record after.

Make sure there's a Linked invoice link on the invoice. This shows the converted estimate. QuickBooks won't create a separate transaction.

This is how you can manage your DO in QBO.

When you're ready to record the payment received from a customer, you can use the Receive payment feature from the + New button in QBO.

Feel free to comment if you have other concerns with creating sales and expense transactions. I can help you anytime. Stay safe and have a nice day ahead!