Open a partita IVA on 20 December and you keep €1,621 less

Two people do the same work for the same clients at the same rate. One opens a partita IVA on 20 December 2026, the other waits and opens on 1 January 2027. Both are on Italy’s flat-rate regime and both qualify for its 5% start-up rate. Run them to the end of 2031 and the one who started twelve days earlier — and billed twelve days more — has kept €1,621.10 less.18

The reason is one clause. The discount is granted “per il periodo d’imposta in cui l’attività è iniziata e per i quattro successivi” — for the tax year in which the activity began and the four after it. A tax year for a person is a calendar year, so the five years always end on a 31 December, whatever date they started on.1

A calendar, not a clock

The Agenzia delle Entrate’s own instructions for the return that reports this income put the rule the same way: the reduced rate applies “per il periodo d’imposta in cui l’attività è iniziata, e per i quattro anni successivi”.2 Its plain-language page for taxpayers describes the same benefit as running “per i primi cinque anni di attività” — the first five years of activity, which is the reading most people arrive with, and the reading a December start breaks.3

Opened on 1 January 2026, the discount covers 1,826 days. Opened on 20 December of the same year it covers 1,473 — the same five tax years, minus the eleven and a half months already spent. Opened on 1 January 2027 it is back to 1,826. The window does not shorten as the year goes on so much as refill on New Year’s Day.8

What the date is worth

Comparing the two people needs one thing held fixed, so both bill at the same daily rate — €50,000 a year, the professional 78% coefficient, INPS Gestione Separata, no business costs — and both stop on the same day, 31 December 2031. The December starter bills twelve days more than the January starter over that window. They also spend a discounted tax year on those twelve days, so 2031 is taxed at 15% for them and at 5% for the person who waited.5

A full year at 5% instead of 15% is worth €2,883.27 in net income at this billing. The twelve days of December are worth €1,643.84 of revenue, of which €1,262.17 survives tax and contributions. The difference — €1,621.10 — is what the earlier start costs, and it is a cost the calendar imposes rather than the tax rate.

Which way it goes depends entirely on how much of the year is left. On 1 January the stub period is the whole year and opening now beats waiting by €35,508. The advantage narrows by about €105.18 a day, all year, and runs out in the first week of December.

Twenty-seven days

The crossing point is 27.41 days of trading left in the year. Above that the stub period earns more than the discounted year it uses up; below it, less. For 2026 that makes 4 December the last date on which opening still pays for itself, and 5 December the first on which it does not.9

That threshold does not move with how much the person bills. Both sides of the comparison are proportional to the rate of billing — a bigger business gives up a bigger discounted year and earns a bigger stub — so the rate cancels and 27.41 days is the answer at €15,000 and at €85,000 alike. What the rate does change is the euros: the year given up runs from €864.98 to €4,901.56 across that range.

It does move with the activity. The share of revenue the regime treats as profit is 78% for professional work and 40% for food, drink and retail, and the whole comparison scales with it: on the tax side alone the break-even is 12.25 days at 40% and 31.19 days at 86%, which would put the December question out of reach for a builder from the first of the month. Read those as the tax mechanism only — the non-professional groups belong to the artisan and trader schemes, whose contributions are not the rate used here.1

The ceiling shrinks with the year too

A second rule is keyed to the same calendar. The regime is open to people whose receipts in the previous year, “ragguagliati ad anno” — restated as a full year — did not exceed €85,000. The Agenzia settled what that means for a business that started mid-year in a 2019 circolare: the limit “deve essere ragguagliato all’anno nel caso di attività iniziata in corso di anno”.14

So the twelve days from 20 December carry a ceiling of twelve days’ worth of €85,000: €2,794.52. Someone who opens on the 20th to get the year started, and cashes a €4,000 advance before the 31st, has receipts that restate to €121,666.67 a year. The regime ends for them from 1 January.8

The two rules close on each other. Paying for the discounted year takes €3,755.13 of stub billing at this profile, and from 16 December the annualised ceiling on the days that remain is smaller than that. There is no amount to invoice in the last two weeks of December that both justifies opening and keeps the regime — bill enough to be worth it and the annualisation puts you out. The date that squeeze arrives depends on the billing rate, and for a business at the top of the regime it arrives on 4 December, the same day the arithmetic turns.9

Losing the regime is the more expensive of the two outcomes by some distance. At €50,000 of billing, a year on ordinary IRPEF instead of the 5% rate is €11,194.37 of net income — near four times the discounted year the December start was spending. The regime stops from the year after the one in which the test fails, and the five discounted tax years do not pause and wait: they are the year of commencement and the four following, in force or not.16

INPS charges by the month

The contribution side of the same twelve days behaves differently, and the contrast is the clearest test that the tax rule is doing something unusual. A professional in Gestione Separata pays a percentage of income and nothing else, so a stub year costs a stub year’s contributions.5

Artisans and traders pay a minimum whether they earned it or not, and there INPS states the price of a partial year explicitly: for periods shorter than the calendar year the contribution on the minimum works out at €376.78 a month for an artisan and €384.31 for a trader in 2026. Opening in December costs them a month of it and no more.7 The pension side of a late start, and the relief that used to soften it, are a separate piece.

One institution prices a fraction of a year as a fraction of a year. The other counts the year and moves on.

What this does not settle

The comparison assumes a constant daily rate of billing, which no real business has. A December that would invoice nothing changes nothing about the argument — the stub earns zero, and waiting wins by the whole discounted year. A December holding one large project fee is the case the annualised ceiling was written for.

It also assumes the person qualifies for the 5% rate at all. Comma 65 attaches three conditions: no artistic, professional or business activity in the three years before, no continuation of work previously done as an employee, and a revenue test where an existing business is taken over.1 And it assumes five years of trading in the regime at a steady rate. Someone who leaves the regime, stops trading, or grows through the €85,000 ceiling before the fifth year gives up less than the figures here; someone whose billing grows gives up more, because the year at the far end is the largest one.

Cash timing is a separate matter again: a business that opens in December files a return for that stub year, and the payments on account that follow the first full year are their own arithmetic. Nothing here is advice about a particular start date — it is what the rules produce for one profile, and the table below is the whole of it, day by day.