I appreciate you for providing a screenshot to us to help resolve your issue, @Kiarie. I'm here to ensure you're able to add the VAT Rate and VAT Amount columns in QuickBooks Desktop (QBDT) Premier Accountant 2018. 

First, let's make sure you've set up the tax tracking feature in the program. This lets you easily monitor your VAT on the invoices. I'll guide you how. 

1. Go to Edit from the top menu. 
2. Select Preferences. 
3. Go to Sales Tax from the left panel. 
4. Choose Company Preferences. 
5. Click Yes beside Do you charge sales tax?.
6. Hit Add sales tax item. 
7. Select Sales Tax Group. 
8. Enter the necessary information. 
9. Click OK. 

For detailed instructions, check out this article: Set Up Sales Tax in QuickBooks Desktop. This link is specific to the UK version, but it also applies to the Singapore version of QBDT. 

Second, let's go to the Additional Customisation window so you can add the two columns. Here's how: 

1. Go to Lists from the top menu. 
2. Select Templates. 
3. Locate and double-click the invoice template. 
4. Choose Additional Customisation. 
5. Enter VAT Rate and VAT Amount under the Title column in the Rate and Amount sections. 
6. Click OK. 

The screenshot below shows you the last three steps. 

Once done, you'll be able to see the VAT Rate and VAT Amount columns on the Invoice screen. View the screenshot below for your visual reference. 

Additionally, I'd suggest visiting this website: Form Templates Overview. You'll find steps on how to customise, duplicate, export, or import templates in the software. 

Also, you can run your sales tax reports to review your VAT payable, such as Sales Tax Liability report. This ensures everything is correct before paying VAT to the appropriate tax agencies. Just go to Reports from the top menu and select Suppliers & Payables. 

I'll be right here to help if you need further assistance. Have a great rest of your day, @Kiarie.