B2B Calculator

15,000 a month on B2B leaves 9,300 to 9,707, and the tax form decides where

A B2B invoice is revenue, not pay. Before any of it is yours it has to cover costs, social ZUS, the Labour Fund, the health contribution and income tax, and the tax form you chose sets the last two. On 15,000 PLN a month with 1,000 of costs and full ZUS, the lump sum leaves 9,707, the tax scale 9,423 and the 19% flat tax 9,300.

How it works

• Takes a monthly invoice amount net of VAT and runs a full year, so the 120,000 scale threshold and the lump-sum health tiers apply the way the annual return applies them.
• Deducts social ZUS at the level you pick (start relief, preferential or full) and the Labour Fund, then the health contribution for your tax form, then income tax.
• Shows VAT separately: it is on the invoice, but it belongs to the tax office.

ZUS 2026, per month: full (base 5,652) 1,788.29 social + 138.47 Labour Fund
  preferential (base 1,441.80) 456.18 · start relief 0

lump sum: tax 12% × (revenue − social − ½ health)
  health 498.35 / 830.58 / 1,495.04 for annual revenue up to 60k / 300k / above
flat tax: income = revenue − costs − ZUS
  health 4.9% of income (min 324.41); tax 19% × (income − health, max 14,100 a year)
scale: health 9% of income (min 324.41)
  tax 12% up to 120,000 a year, 32% above, minus 3,600

Worked example

15,000 PLN a month invoiced net of VAT, 1,000 of monthly costs, full ZUS, twelve identical months.

1. full ZUS with the Labour Fund: 1,926.76 a month under every form
2. lump sum at 12%: health 830.58, tax 1,535.57, net 9,707.09
3. flat tax: income 12,073.24, health 591.59, tax 2,181.51, net 9,300.14
4. tax scale: health 1,086.59, tax 1,563.44, net 9,423.21
5. VAT at 23% on top of the invoice: 3,450, passed straight to the tax office

The same work leaves between 9,300 and 9,707 a month. At this level the lump sum wins because its 12% falls on revenue that costs barely reduce; with large costs, or a lump-sum rate above 12%, the order changes.

Reading the result

• The lump-sum rate follows the activity, not your preference. 12% covers most programming and IT services, while other services sit at 8.5%, 15% or 17%. The calculator uses 12%, so check the rate for your activity code first.
• The form can be changed once a year, by 20 February, or when the first income of the year arrives. The comparison is worth running in January, not after.
• Sickness insurance is voluntary for the self-employed. The calculator includes it, because without it there is no sick pay; leaving it out saves 138.47 a month on full ZUS.
• The figures assume twelve identical months and no other income. The tax-free amount, the 120,000 threshold and the health tiers are annual, so an uneven year or a second job changes the result.

Common questions

How much ZUS does a sole trader pay in 2026?

No social contributions for the first six months (start relief), then 456.18 PLN a month for 24 months on preferential ZUS, then 1,926.76 PLN a month on full ZUS. Those figures include the voluntary sickness contribution and, for full ZUS, the Labour Fund. The health contribution comes on top and depends on the tax form.

Is the lump sum or the flat tax better for a programmer?

At the 12% rate the lump sum usually leaves more, because it charges less on revenue than the flat tax charges on income. The flat tax starts to win when deductible costs are large or when your lump-sum rate is higher than 12%. Enter your own costs and compare all three forms here.

Should the invoice amount include VAT?

No. Enter the amount before VAT. If you are VAT registered, the 23% added on top is collected for the tax office and paid over in your VAT return, so the calculator shows it separately and never counts it as income.

Sources

• podatki.gov.pl — Ministry of Finance tax portal
• ZUS — contribution bases and rates