Choosing the 2027 form of taxation: the comparison belongs in November, the CEIDG change by 20 February

The Deadline Is in February. The Data Is Already Here.

A sole trader who wants to change their form of taxation for 2027 has until the 20th of the month after their first revenue of the year. For almost every client that means 20 February 2027. If the first revenue only comes in December, the deadline moves to the end of the year. The change goes through CEIDG, it costs nothing, and if nobody files anything the client simply stays on this year's form.

That deadline is why most offices have this conversation in late January or early February. It's also why the conversation is usually rushed. January is the month of the year-end close, PIT-11s, the first JPK files under the new rules and every client who suddenly remembers a missing invoice. Nobody has an hour per client to compare three forms of taxation.

But the comparison doesn't need January. It needs the client's 2026 numbers: revenue, costs, social contributions, and a reasonable projection of 2027. By the end of October, ten months of that are already in the KPiR or the lump-sum register. The calculation can be run in November, and the conversation can happen while the client still has time to think.

The Same Client, Two Answers

Take a sole trader providing services to companies. Their 2026 income, after social ZUS contributions, is projected at 200 000 zł. To keep the arithmetic readable, I'll compare tax plus health contribution only.

Tax scale. 12% on the first 120 000 zł minus the 3 600 zł tax-reducing amount, then 32% on the remaining 80 000 zł: 14 400 − 3 600 + 25 600 = 36 400 zł of tax. Health contribution at 9% of income: 18 000 zł, not deductible. Total: 54 400 zł.

Flat 19%. Health contribution at 4.9%: 9 800 zł, which is below the annual deduction cap, so it reduces the tax base. Tax: 19% × 190 200 = 36 138 zł. Total: 45 938 zł.

On those numbers the flat tax wins by 8 462 zł, and that's where most spreadsheets stop.

Now add one fact the spreadsheet doesn't have: the client is married, and the spouse has no income. On the scale they can file jointly. The 200 000 zł is split in two, each half taxed at 12% minus 3 600 zł: 2 × 8 400 = 16 800 zł of tax. Add the same 18 000 zł of health contribution: 34 800 zł. That's 11 138 zł less than the flat tax. The "obvious" switch to 19% would have cost the household more than eleven thousand złoty a year.

Joint filing and the child relief exist only on the scale. A comparison that doesn't ask about the spouse and the children isn't a comparison. It's a guess with two decimal places.

Where the Lump Sum Fits

For lump-sum candidates the question is different: how large are the costs? Take a client whose activity falls under a 12% rate. On tax alone, the lump sum and the flat tax are equal when 12% of revenue equals 19% of revenue minus costs. That happens when costs are about 36.8% of revenue (1 − 12/19). Below that, the lump sum costs less. Above it, the flat tax or the scale is cheaper, because the lump sum ignores costs entirely.

A programmer with 300 000 zł of revenue and 30 000 zł of costs is far below that line. A contractor buying materials for 40% of revenue is above it, whatever the rate looks like on paper.

Two things make the lump sum harder to calculate in November than the other forms:

• The rate depends on the activity, not on the client's PKD code alone. The same client can have revenue at 8.5%, 12% and 15%. Somebody has to decide which revenue belongs where, and that's the accountant's call.
• The health contribution is a flat monthly amount in three revenue bands (up to 60 000 zł, up to 300 000 zł, above 300 000 zł), based on the average wage for the fourth quarter of the previous year. For 2027 that's the Q4 2026 figure, which GUS publishes in January. Under the current rules the 2027 amount doesn't exist yet in November, so any comparison has to use this year's amount and say so.

And one hard limit: the lump sum is only open to clients whose 2026 revenue stays within 2 million euro. For 2027 that's 8 754 000 zł. A client near it shouldn't get a lump-sum recommendation in November without a note about December.

How Many Clients This Is

A typical office of the kind I work with has around 120 clients: maybe 25 on full books, 60 on KPiR, 35 on the lump sum. The form-of-taxation question concerns the 95 individuals and partners. In my experience, for 15 to 20 of them a different form would save more than 3 000 zł a year on the numbers alone. For a few, the answer flips once you ask about the family.

Doing it properly by hand takes 20 to 40 minutes per client: export ten months of the ledger, project November and December, calculate up to three forms, check eligibility, write it up. For 95 clients that's three to five working days. So it doesn't happen, and the January conversation becomes "do you want to stay as you are?"

The mistakes are the same every year:

• The comparison ignores health contributions, or uses one rate for all forms. The difference between 9% and 4.9% of income is the whole story for many clients.
• Nobody asks about the household. Joint filing and the child relief disappear the moment a client moves off the scale.
• The projection is ten months times 1.2. A client with a seasonal December, or one who just lost a large customer, gets a confident answer to the wrong question.
• The client hears about it on 15 February and decides in five days.

What the Agent Prepares

An agent with read access to the client's KPiR or lump-sum register can do the assembly in November, as part of the month-end close the office already runs:

• Reads the 2026 figures from January to the last closed month: revenue, costs, social contributions, the current form and, for lump-sum clients, revenue split by rate as the office recorded it.
• Projects the full year from the last twelve months rather than multiplying, so a strong or weak December shows up.
• Calculates tax plus health contribution for every form the client is eligible for, with the eligibility checks spelled out: the lump-sum limit, and the former-employer restriction, which works differently for each form: the flat tax is closed for services to an employer when the client did the same work for them under an employment contract in the same tax year, while the lump sum also looks back to the previous year.
• Flags clients where another form saves more than a threshold the office sets, say 3 000 zł, and clients near a threshold where the answer is fragile.
• Writes the questions the numbers can't answer: does the spouse have income, are there children, is a large purchase planned for 2027, is a big customer leaving?

The agent doesn't recommend a form, doesn't touch CEIDG and doesn't decide which lump-sum rate applies. Those are the accountant's decisions, made with the client. Its job is to put a one-page sheet on the accountant's desk in November instead of an empty spreadsheet in February.

One Thing to Do This Week

Pick five clients you'd guess are on the wrong form. For each, write down two things: projected 2026 income, and whether the spouse has income. If you can't fill in the second column, that's the conversation to schedule before Christmas.

If you'd like to see the November comparison run on your own clients' ledgers, write to me. I'll take one month of real data and show you which clients the agent flags and why.