Can we have adjustable tax (VAT) for our individual invoices or do I need to go every time in the billing settings (BILLING > SETTINGS) to adjust it?

Yes, you can adjust the tax individually for each client in their profile: CONTACTS > CONTACT NAME > “Edit Info” > Billing Settings > check the option “I want to use a different VAT” then “Custom Tax Value (%)” > enter the specific value in the field (only the number, no need for the percent symbol) > and save the change.

Please read and consider carefully the prompt message displayed when you save the VAT change: “This change affects your client agreements, billing, invoices and product sales. Are you sure you want to change this setting? You may have to edit/delete existing agreements and payment plans, reset automatic invoices and recurring payments, etc.”