Interest, paying with the F24 form, and special cases

Giulia, a graphic designer in Bologna, missed a €5,000 tax payment at the end of November 2025 and puts it right in February 2026. Her interest is not a single figure: forty days of delay fall in 2025 at 2 per cent, fifty in 2026 at 1.6. That comes to €21.92 in all, to be entered on the F24 form on a separate line from the tax.

Interest: a single formula

The Agenzia's page gives the formula in full: tax to be paid, multiplied by the statutory interest rate, multiplied by the days of delay, divided by 36,500. The divisor combines two steps, the hundred that turns the rate into a percentage and the 365 days of the year. This is simple interest, worked out on the tax alone.

Interest runs from the day the payment should have been made until the day it is actually made. It is not charged on the penalty and is never reduced: ravvedimento cuts the penalty, not the cost of time. The rate is the one under article 1284 of the Civil Code, which is set each year.

The rate changes every year, sometimes sharply: the same page lists 0.01 per cent for 2021 and 5 per cent for 2023. That is why the rate to use is not the one in force on the day of payment, but the one for each year in which the delay built up. Picking the wrong year can multiply the interest.

Counting the days is where most errors creep in. The delay runs from the deadline to the day payment is actually made, not the day the form is prepared. Anyone who does the working on Monday and pays on Thursday must redo it, because the interest changes and sometimes the penalty band does too.

A delay spanning two years

When the deadline falls in one year and the payment in the next, interest is worked out in two segments: the first year's days at that year's rate, the second year's at the new rate, then added up. The ActioFin calculator, which only knows the 2026 rate, does not take such cases and asks you to split them.

The penalty, on the other hand, is not split. What counts is the total delay, ninety days for Giulia: a base penalty of 12.5 %, or €625.00, reduced to one ninth because payment arrives between the thirty-first and the ninetieth day. That makes €69.44, added to the tax and the interest.

Which F24 form to use

Ravvedimento is paid with the same instrument as the forgotten tax. The Agenzia names the F24 form for income taxes and the related substitute taxes, VAT, IRAP, the entertainment tax and registration tax on deeds other than leases, always together with penalties and interest.

For taxes, penalties and interest linked to registering property leases and rentals, the F24 Elide is needed instead: the form carrying identifying details. The same form is used for mortgage tax, mortgage fees and stamp duty owed for land registry services and for the issue of certificates and copies.

On the form each sum goes on its own line. The tax keeps its own tax code, while interest and penalties have dedicated codes, which the Agenzia gathers in a full list. The exception is a withholding agent putting right a withholding tax: the interest is added to the tax on the same line.

How to pay: channels and obligations

People without a VAT number can choose. The paper form is handed in at a bank, a post office or a collection agent's counter, paying in cash, by cheque, by card or by debit to one's own account; the online route is available too. Holders of a VAT number, by contrast, must submit the F24 exclusively online.

The online route runs through the Agenzia's F24 web and F24 online services, using Entratel or Fisconline credentials, through the home banking of approved intermediaries, or through an authorised intermediary. Anyone offsetting the credits listed on the Agenzia's page, and anyone submitting a nil-balance F24, must go through the Agenzia's own online services.

Amounts are always written with two decimals, even when these are zero: seventy euros become 70.00. If the working produces more decimals, the second digit is rounded, up if the third is 5 or more and down if it is lower. That is the rule that turns €1.9726 of interest into 1.97.

Mistakes on the form, and how to fix them

According to the Agenzia, the most frequent errors when filling in the form concern three fields: the tax code, the reference period and the tax identification number. To fix a mistake already transmitted there is the Civis F24 service, which collection intermediaries can also use for payment orders submitted on behalf of their clients.

The reference year field states the year the payment relates to, written with four digits. In a ravvedimento it is easy to confuse it with the year of payment: a tax relating to 2025 that is put right in 2026 still refers to 2025. This is the detail that most often lands a correct payment on the wrong period.

A separate case is the forgotten nil-balance F24, where offset credits exactly match the debts. Even with nothing to pay, failing to submit it carries a €100 penalty, cut to 50 if the delay does not exceed five working days. The breach is put right through ravvedimento, by submitting the missing form.

The Agenzia gives the figures already reduced: €5.56 within five days, one ninth of 50; €11.11 within ninety days; €12.50 within one year; €14.29 within two years; €16.67 beyond that; €20 after an inspection report. They are paid under tax code 8911, alongside submission of the missing form.

The right section, the right line

The F24 form is divided into sections, and a ravvedimento goes in the section of the tax it puts right. IRPEF, IRES, VAT, withholding taxes and state duties go under Erario; IRAP and the regional IRPEF surcharge under Regioni; municipal taxes under IMU and other local taxes. Penalty and interest follow their tax.

Some sections ask for one more item. The Regioni section needs the code of the region entitled to the payment; the local taxes section, the cadastral code of the municipality. The taxpayer section carries the tax identification number, personal details and tax domicile, plus a co-obligor where the case calls for one.

For the main return-based taxes paid in a single amount, the Agenzia asks for 0101 in the instalment column. When an heir, parent, guardian or curator pays, the taxpayer section carries the details of the person paid for, and the payer's tax number goes in the dedicated box with its identifying code.

Giulia's form carries three lines and a single total. The tax code for each line comes from the Agenzia's list, starting from the code of the original tax: this course does not reproduce them, because they differ from one tax to another and a wrong code sends the money to the account of a different tax.

Paying in parts: partial ravvedimento

Someone who cannot pay everything at once can put things right in instalments. Article 13-bis of Decree 472 of 1997 allows it, for taxes run by the Agenzia delle Entrate only, even when the amount due is paid in several parts, provided the time limits set for each reduction are met.

The reduction depends on when the penalty itself is paid. One may settle the penalty for each separate payment with the fraction valid on its date, or pay it in one go with the reduction applicable on that day. Each part of the tax carries its own interest up to the day it is paid.

A five-step routine

• establish the date of the breach, to choose between the old and new regimes
• count the days of delay from the deadline to the day payment will be made
• set the base penalty and the reduction fraction, then work out the reduced penalty
• work out interest at the statutory rate of each year involved
• fill in the F24 with tax, penalty and interest on separate lines, each with its own code

The ActioFin ravvedimento calculator carries out steps two to four for a delay falling entirely within 2026, for a single omitted or late payment and with no official act involved. It shows the full penalty, the fraction applied, the reduced penalty and the interest, with the formula behind each line.

Keep the F24 receipt together with the working. Should the Agenzia ask about the payment, the two documents show that the ravvedimento was carried out in full and with the levels then in force. The rules described here are those read on the Agenzia's pages in September 2026.