how would i add extra tax, MAT 4% on and invoice ?

Hello, @klcdcoffice. You can add an extra tax by first setting up a custom rate within your sales tax settings. Just navigate to All apps > Sales Tax > Manage sales tax > Add tax. Next, click the Add button under the Add a custom tax and agency section on the following screen. Then, fill in the required fields and hit Add to complete the process. 

Afterward, you can now select it from the Sales tax column dropdown on your invoice. This automates the calculation and organizes your records. On top of that, you also have an option to pull up your Taxable Sales Summary anytime to ensure everything is accurate before filing your return. 

For follow-up questions, leave a comment below.