a. Is it a similar process in Poland?
Cheers for that, best laugh I've had all day! You pay ZUS (social security) monthly, tax monthly or quarterly and VAT monthly or quarterly. Then you do an annual return and pay up or get a rebate as appropriate. You will
need an accountant.
b. Do I need to apply for a tax file number or something like that when I first arrive?
Yes. You need a NIP number and a PESEL number.
c. Do I have to register my business with a Polish government body? If so, how and with who do I do that?
First you need permission to be self-employed. Details here paiz.gov.pl/index/?id=866d90e0921ac7b024b47d672445a086
Then you go to the GUS (national statistics office) and register there to get your REGON number. Then you go to ZUS and register there. Then you go to the tax office and register there and then again for VAT (different office). Then you go to a stamp shop and have your company stamp made. Then you go to a bank and open a business bank account. Simples.
d. What is the taxable percentage on my gross income?
19% less your business expenses.
e. Is there a system where you do not pay tax on the first amount? (for example when I lived in England I think it was something like the first £4500 was tax free, then the next £2000 was something like 10% tax, and then anything above that was taxable at 22%. However I can not remember the exact figures).
You can have stepped rates as a self-employed person but if you earn more than about 50,000zl per year, you don't want them: you want the flat 19%
f. Also, what about paying your ZUS (which I assume is something like NI in the UK) - how do I pay that as a self-employed worker?
Your accountant will tell you how much you need to pay to each of the three accounts and then you make transfers. You could try doing it without an accountant but good luck to you: you'll need it!