The key is that at the tax office you need to express 'active regret' that your taxes have not been paid
well if i understand correctly, she worked in 2008, and the tax reports for 2008 aren't due till the end of april so there's no reason she should express any active regret just yet (especially that it doesn't exist enymore, now all you can do is provide written explanation and ask not to be fined - same thing but different name), cause she hasn't done anything wrong. but her employer should've given her a pit-11 (sth like the w-2s in the us) form, which for her is the basis to do the tax report with the polish irs. the employers responsibility was to hand this to her till the end of feb. since it hasn't been done, what she should do is to gather all the salary slips (or bank statements)- if there are any, or any kind of correspondence regarding payment for her services or billing for the classes, i mean ANYTHING that might implicate that the emplyer acknowleged that she works for him. and find a good accountant or take sb she can trust to the irs and ask them to investigate why she hasn't received any pit-11 yet, if there is any pit-11. Most likely there isn't any cause obviously the employer made her work under the table.
just gather everything u can - contract, promise of a contract, e-mails, bank statements and just squeal on the mofos. dont even tell them ur going to do it just do it. if you can't gather enough evidence simply pretend that nothing happened for now and in the e-mails inquire about the salary, legitimacy of your employment - but so they don't figure out why. and if they admit to anything in writing take it as a proof with you.
and yes - this is common with the english schools. my husband went through tax BS every year with different employers. but in his case there was no problem with the legal work cause he had a temporary residency card. and always after he threatened to inform the tax office about the matter they would give him his tax forms :@)
so if u wanna make your employer's life miserable (which i would if i were you) - do it. he deserved it.
or just get a ticket home and before you leave break all the windows at his school ;@P