Firstly, tax withholding must be enabled within the invoicing settings.
Click "Settings" in the side menu on the left.
The side menu switches to Settings mode and shows the sections for your personal profile, and company profile. From here, click on the option for "Invoicing".
Once selected, scroll down the page until you see the option "Enable Tax withholding". Click here to activate the function, and Tax withholding will then become enabled.
Next, open the invoice you need to add tax withholding to. Then, in the bottom right corner, click on "Apply tax withholding".
A pop-up window will open. Click on the toggle “Tax withholding” and then select the reason of withholding from the drop-down menu. The percentage in the fields Rate and Taxable will change automatically.
Now your invoice is ready to be sent to your customer!