If you invoice, you have to pay taxes. Taxes vary from industry to industry. For example, the tax on catering is 3.5, the tax on tobacco industry is relatively high, reaching 12.5, and there is value-added tax. Merchants are reluctant to issue invoices.

In the latter case, the tax bureau can't receive as many invoices as you said. If you can't get enough invoices, of course it's not enough.