Paying June's INPS bill on day 120 costs €124.01

A professional on Italy’s flat tax who settles June’s pension contribution on the 120th day after the deadline owes €124.01 for the delay, at the rate that takes effect on 16 September. The hundred and twenty days are a real concession and they are not a free pass: article 116, comma 8, lettera a) of L. 388/2000 says the maggiorazione of 5.5 points non trova applicazione to a contribution paid inside them. It does not say the charge those points are added to stops.1

INPS put the two rates side by side on 11 September. Its circolare 98 records that the European Central Bank lifted the rate on its main refinancing operations — the successor to the tasso ufficiale di riferimento, and the rate this statute points at — by a quarter of a point on 10 September, to 2.65% from the 16th. From that date a late contribution carries 8.15% a year once the window has shut, and 2.65% a year while it is open.2

The dash in our own table

The piece that costed a missed 30 June printed a dash against every day inside the window, and said in its closing section that it was pricing the 5.5 points and nothing else, because the rate underneath was fixed by neither of the statutes it worked from. That was accurate and it was incomplete: a reader totting up a late June got a table whose first four months read as nothing owed. The September circolare supplies the missing rate, so the rest of the charge can be put on the same bill.

The bill is the one already published for that morning — €14,234.22 of Gestione separata contribution falling due on 30 June of a practice’s second calendar year, billing €50,000 on the 78% coefficient.34 Holding that contribution fixed, the charge for lateness is 2.65% of it in ragione d’anno — quoted as an annual rate and accrued over the days that have actually run — until the window shuts, and 8.15% over the whole elapsed period after that.

A year of delay costs €1,160.09 rather than the €782.88 the 5.5 points reach on their own. The €377.21 between them is the reference rate doing its work from day one, and it is roughly a third of what the twelve months are charged.

The ceiling moves with it. The sanction cannot pass 40% of the contribution, which on this one is €5,693.69; at 8.15% a year that ceiling arrives after four years and eleven months, where the 5.5 points alone take seven years and three months to reach it.

The rate moved while the clock was running

One number in that table is doing something the others are not. €124.01 holds 2.65% across all hundred and twenty days, and a delay that began on 30 June 2026 does not run at one rate: the increase takes effect on 16 September, so 78 of those days fall under the 2.40% before it. Charging each stretch at the rate in force over it — which is how the circolare dates its own measures, “a decorrere dal 16 settembre 2026” — gives €116.41 instead, and €1,152.48 instead of €1,160.09 at a year.2

So the rate change moves the figure by about six per cent at four months and under one per cent at a year, and it does not reach the thing being reported. Both bases charge something on day 30 and something on day 120. Whichever is used, the window is not a period in which nothing is owed.

Paying it in instalments gives the window up

The concession is narrow on its face: the payment has to be within a hundred and twenty days, in a single sum, made spontaneously, before the institution has asked for it. An instalment plan satisfies none of that, and the same circolare prices the alternative — interest on a rateazione presented from 16 September runs at 4.65% a year, which is the reference rate plus two points since a March 2026 decree cut that addition from six.2 Two points is not five and a half, but it is charged on a debt that also carries the full sanction, and the single payment inside the window is the only route that avoids the 5.5 points altogether.

What this does not settle

The rate is not a fixed quantity. It follows the European Central Bank’s policy decisions, it moved on 10 September, and a delay long enough to reach the ceiling would straddle a good many more of them. The figures here are what the rates in force from 16 September 2026 produce on one contribution, not a forecast of anybody’s bill.

Everything above is the omission case — a contribution whose amount is visible on the return that was filed, and simply paid late. Where a return is missing or untrue, lettera b) charges 30% a year against a 60% ceiling, and none of these numbers carries across.1 The tax half of the same June bill is governed by a different statute again and is unaffected by any of this; it still carries interest at the legal rate on top of its own reduced sanction, and that is not priced here either. This is what the rules produce on one worked contribution, not advice about what to pay or when.