Same €4,000 a month: a builder bills €13,025 more

A shop that bills €56,032 in a year and a builder who bills €69,057 end the year with the same money: €4,000 a month, once contributions and tax have gone. The builder works through €13,025 of extra billing to arrive at the same place, and the reason is the activity code each of them registered.

Italy’s flat-rate regime does not tax profit. It treats a fixed share of everything you invoice as income — 40% for a retailer, 78% for most professionals, 86% for construction — and taxes that share at 15%, or at 5% for the first five years of a new activity. That share, the coefficiente di redditività, is set by the activity group in the statutory annex and not by what the business actually earns.12 Contributions are subtracted before the tax is worked out, and they are the larger of the two bills.

What €4,000 a month costs in billing

Running that arithmetic backwards — fix the cash, solve for the invoice total — gives one answer per band. The seven below are every distinct combination of statutory share and contribution scheme a person on this regime can be in, on 2026 rates, with the tax at 15% and no business costs subtracted.3

A professional on the 78% share — the band that covers consultancy, engineering, health and teaching — needs €67,591. Of that, €52,721 counts as income, €13,744 goes to INPS, and €5,846 is the substitute tax.5

Why the same money costs different billing

The obvious explanation for the spread is that the seven cases pay into different pension schemes on different terms, and that would be a fact about INPS rather than about the flat tax. It is worth about a thousand euro. Hold the statutory share at 67% and move the person between all three schemes and the billing needed for €4,000 a month runs €62,933 as an artisan, €63,159 as a trader, €63,912 in the Gestione Separata.

Hold the scheme still instead and move the share, and the answer runs from €56,380 at 40% to €70,544 at 86% — a spread of €14,164, wider than the €13,025 the two real cases differ by, because the artisan scheme costs the builder €1,487 less than the Gestione Separata would. The band is doing the work.

Where the regime runs out

The regime itself stops at €85,000 of billing.1 That puts a ceiling on what it can ever pay out, and the ceiling is a different height in every band: bill the maximum and a retailer keeps €6,068 a month, a builder €4,914.

So €5,000 a month is not available to a builder on these terms. The arithmetic asks for €86,492 of billing, and the €85,000 line stops it €1,492 short. A professional on 78% makes it with €512 to spare. What the regime pays above the ceiling is not this arithmetic continued but the ordinary tax rules, which take a step down at the same line.

Two provisions move the builder’s line back inside. The 35% cut in contributions that artisans and traders may ask for brings €5,000 a month down to €79,360 of billing, at the price of pension months when the presumed income is low — priced in an earlier piece on that discount.1 The 5% start-up rate, available for the first five years, brings it to €79,008. Both are conditional, and neither is available to the professional on the Gestione Separata: the 35% cut reaches artisans and traders only.

At the bottom, the contribution stops shrinking

The ladder is not proportional at the other end either. Artisans and traders owe their pension contribution on a minimum income of €18,808 however little they make: €4,521.36 for an artisan, €4,611.64 for a trader, both including the €7.44 a year for maternity cover.4

A retailer aiming at €1,500 a month bills €23,319, which the 40% share turns into €9,328 of presumed income — half the minimum, and the contribution is charged as though it were the whole of it. Doubling the target to €3,000 takes €42,468 of billing rather than twice €23,319, because the fixed part of the bill has already been paid. Someone in the Gestione Separata has no such floor and pays 26.07% of whatever the presumed income comes to. On the same 67% share that reverses the order twice over: at €1,500 a month the Gestione Separata case needs €23,967 against the artisan’s €24,284, and at €5,000 it needs €79,890 against €78,664.

What this leaves out

Every figure above is before the money spent to earn it, which is how the question is usually answered and is not how a year works. The flat rate never reimburses a real cost — the statutory share is the cost allowance, so a euro spent reduces the cash and not the tax.

Put 10% of turnover through the business and the professional’s €4,000 a month needs €78,668 instead of €67,591. At 20% it needs €94,089, which the regime does not allow, and the honest answer to the question becomes that this regime cannot pay it. For construction, where materials make a light-cost year unusual, the same 20% asks for €97,344. Where costs run that high the ordinary regime can be the cheaper of the two, and we have priced the crossing point.

Three more limits. The 78% row assumes the professional is insured with the Gestione Separata; a lawyer, an engineer or an accountant pays their own professional fund instead, on that fund’s rules, and the arithmetic changes. The calculation is a settled year, with the contributions and tax of one year paid in that year — the first two years do not work like that, which another piece sets out. And it is turnover, not billing you have chased: money that arrives in January is January’s.

How this was worked out

The regime’s arithmetic runs forwards — billing, statutory share, contributions, substitute tax, cash. Fixing the cash and searching for the billing that produces it is a bisection over that same chain, run for eight monthly targets, seven band-and-scheme combinations, both tax rates and with the 35% contribution cut on and off: 192 rows, all published below.

The Gestione Separata cases go through the same engine as the calculators on this site, and the artisan and trader cases through the rates INPS published for 2026, checked by reproducing the contribution the circolare itself prints for the minimum income. One thing had to be fixed along the way: the first version of the search ran over the real net-income curve, which falls at €85,000 when the regime is lost, and a bisection over a curve that falls lands on the wrong side of it — it reported €128,916 for a case whose answer is €78,140. The search now solves the flat-rate arithmetic and marks anything past €85,000 as out of reach, which is what the last column of the table means.