The modelo 303 is the quarterly IVA return: the difference between the IVA you charged your clients and the IVA you paid on your expenses. It's filed 1–20 April, July and October, and 1–30 January.
The modelo 303 is the quarterly IVA return. In it you tell the tax office how much IVA you charged your clients and how much you paid on your expenses, and you only hand over the difference.
In other words: you don't hand over all the IVA you invoiced. From the IVA charged you subtract the IVA on your gastos deducibles (that equipment, that software, that work lunch). What's left is what you pay. If you paid more IVA than you charged, it comes out in your favour.
Every quarter: 1–20 April, 1–20 July, 1–20 October and 1–30 January. If you pay by direct debit, the window closes a few days earlier. At year-end you also file the annual IVA summary, the modelo 390.
The 303 becomes easy when you keep two things during the quarter: the IVA you charge and the invoices for your expenses with IVA. You set the first aside; you recover the second. Cece adds them up for you so on filing day there's nothing to reconstruct.
The modelo 303 declares IVA (the tax you charge clients) and the modelo 130 prepays IRPF (the tax on your profit). Both are quarterly, but they tax different things and not every freelancer files both.
Four times a year: 1–20 April, July and October, and 1–30 January. With direct debit the window closes a few days earlier. In January you also file the annual IVA summary (modelo 390).
Cece takes care of what weighs on your day-to-day (projects, payments, proposals, tax calculations) and surfaces the numbers that matter, so they stop weighing on you and you can get back to what counts.
