Adapt invoiceninjia to italian context

Hello,
I Hope that somenone can help my to adapt invoiceninja to italian fiscal context:
Here ad example:
<Products -> €. 1.000,00
Total -> €. 1.000,00
Iva del 22% sul totale compenso – €. 200,80
Total €. 1.200,00 (€. 1.000,00 + €. 200,80)
Held in advance 20% – €. 200,00 [-] (€. 1.000,00 * 20%) [Italian Fiscal manovre] [HERE I DONT’KNOW HOW I CAN MANAGED IT because it’s a subtraction applied after the application of the vat]
Net to pay – €. 1.000,00 [1200,00 - 200,00]

Waiting any suggest.

Thanks in advance.

A.

Maybe you can set a custom invoice surcharge on /settings/invoice_settings#invoice_fields

Got it! Thanks for your help!