Every tax agency form, whether a quarterly self-assessment or an annual return, is laid out in numbered casillas. Some hold data you enter yourself, such as the taxable base of your sales, and others are calculated automatically from earlier boxes, such as the amount to pay or to be refunded. So when an advisor or the tax agency itself mentions a particular casilla, you just look for that number on the form to know which figure it refers to.
The typical mistake is copying box numbers from a previous year or an old guide. The tax agency changes the layout of its forms from time to time, and a casilla can move, split or disappear. Another frequent slip is mixing up boxes from different forms: the same number does not mean the same thing on a VAT return as on an income tax return. If a letter from the tax agency cites a casilla, always check it against the form for the right tax year.
Casillas appear on every form, such as the quarterly VAT return, the income tax prepayments or the census declaration, and in tax agency notices. In kontora forms are prepared casilla by casilla from your accounts and invoices, with deadline reminders, so you can see where each figure comes from before you file it from the app itself with your certificate (303, 130, 111, 115 and 123 by direct filing; 349, 347, 190, 180 and 193 through TGVI) or on the sede electrónica.
Guides that use this term
- Modelo 303: the Spanish quarterly VAT return, explained
- How to fill in the modelo 303 box by box: a practical 2026 guide with a worked example
- How to fill in the modelo 390 box by box: instructions, a full-year example and how to reconcile it with your 303 returns
- Choosing accounting software as an autónomo in Spain: Verifactu, the free AEAT app and eight criteria to get it right
- How to fill in modelo 111 box by box: 2026 instructions with a worked example
Related terms
Rather have this calculated for you?
kontora generates your tax forms box by box, tells you how much to set aside and reminds you before every deadline.