• 1. You did not register company in Poland in the last 5 years,
  
• 2. If you're contractor for your former employer, you can't do the same work for him in current or previous tax year.

• you can take into account the costs incurred and reduce tax in this way. NOTE: This privilege does not apply if you use flat rate tax.
  
• you can give VAT (incluing VAT EU) invoice to your contrahent, which make cooperation with foreign companies much easier,
  
• you get more options to optimize you costs e.g. by choose tax model, which bests your case in the best way (linear tax, progressive tax, flat rate tax).
  

• you're not employee, so you have no any privileges related to contract of employment employment. All depends on contract beetwen your company and your contrahent. So, of course you can negotiate better conditions, but also you can negatiate worse. It's simply your business now.
  
• you need to manage accountancy on your own. Also, you can hire accounting office to do it for you, but it's extra cost.
  
• you're obligated to pay insurance contributions (polish ZUS) each month, no matter if you earn money or not.
  

More about progressive tax:

• Currently (as of 2022) taxpayers who settle accounts on general rules are subject to the so-called tax thresholds. This means that the rate (percentage) of the tax depends on the achieved incomes.
  
• At the beginning of 2022, after the so-called "Nowy Ład" (en: "New Deal") entered into force, the thresholds have been changed, so that income below 120 000 PLN is taxed at 17%. Starting from July 2022 the rate of the first threshold will be reduced to 12%. Income above this amount is taxed at 32% rate (before and after July 1). This means that for the first six months we should count advances on income tax according to the scale of 17% and 32% (before July 1, 2022), and in the second - 12% and 32% (after July 1, 2022).
  
• In Poland, there is a free amount (tax allowance), on which we will not pay tax. For this reason, the final tax will be slightly lower than it would appear from the thresholds. In 2022 the tax-free amount is 30 000 PLN.
  
• The tax base (i.e. the amount on which the tax is calculated) is the sum of revenues obtained in a given year decreased by social insurance contributions contributions (polish: ZUS) and costs of getting incomes:
  
  tax base = gross earnings - social insurance - cost of getting income
  ⚠ WARNING! Beginning from 2022 (→ see "Nowy Ład") we cannot decrease tax by health insurance contribution if we use tax thresholds (general rules).
• Despite the fact that the method of calculating the monthly tax advance changes during the year, the annual tax for 2022 year will be calculated in the unified way i.e. using 12% and 32% rates for the whole year. To calculate annual tax for income earned in 2022 use the following formula:
  
  • if your tax base does not exceed 120 000 PLN:
    $$12\% \times \text{tax base} - 3600$$
    
  • if your tax base exceeds 120 000 PLN:
    $$1440 + 32\% \times (\text{tax base} - 120000)$$
• Because so-called "Polski Ład" (en: "New Deal") introduced in 2022 caused a decrease in the net salaries of selected groups (on-the-hand), the polish rulers introduced the so-called relief for the middle class. This is the amount that should be subtracted from the tax base when calculating the monthly tax advances from January to June 2022 inclusive. However, the rulers gave up this idea and we should stop including this relief after July 1, 2022. To calculate the middle class relief, the we use following formula:
  
  If your gross monthly earnings:
  

  • do not exceed 5 700 PLN - no discount,
    
  • are in the range from 5701 PLN to 8549 PLN:
    $$\text{middle class tax relief} = \frac{\text{gross monthly earnings} \times 0.0668 - 380.5}{0.17}$$
    
  • are within the range from 8550 PLN to 11141 PLN:
    $$\text{middle class tax relief} = \frac{\text{gross monthly earnings} \times (-0.0735) + 819.08}{0.17}$$
    
  • exceed 11141 PLN - no relief.
• Starting from August 2019, people under 26 y.o. in Poland do not need to pay income tax (PIT).
  In 2019: the tax-relief covers annual revenues up to 35636.67 PLN. In 2020, 2021 and 2022 tax-relief covers annual revenues up to 85528 ​​PLN. Revenues exceeding the annual limit remain taxed using tax-scale.