I'm a tourism company operating in the aviation and outbound tourism sectors. Typically, taxes are 0% as our operations are outside the country. However, the state has now imposed a tax on the profit margin. This means if the selling price of an airline ticket is 1100 and the purchase price from the supplier is 1000, the profit is 100. The tax is calculated as 5% of this profit, i.e., $100 * 5% = 5.

How can I fully implement this process in Zoho Books? When I create a sales invoice, it will be for 1100, and when I create the purchase invoice for the supplier, it will be for 1000. The 100 profit only appears in the monthly profit and loss statement. The same applies to projects. How can I make Zoho Books automatically calculate this tax? The selling and purchase prices are not fixed as it's a service, not a product, so using items isn't beneficial for this process.