Modelo 303 is the quarterly VAT self-assessment, where you declare the VAT charged on your invoices and deduct the VAT paid on eligible purchases and expenses. It is filed from 1 to 20 April, July and October, and for the fourth quarter from 1 to 30 January; filing or paying late can trigger surcharges.
Even with no activity in the quarter, the form generally still has to be filed showing a nil result.
kontora generates your tax forms box by box, tells you how much to set aside and reminds you before every deadline.