I don't see how
If you don't have the knowledge of how Polish company taxation works, then I'd steer clear of making assumptions.
it is simply a case of filing vat each month - which is neither complicated to calculate nor (from what I have seen) complicated to file.
Trying to say that Polish accounting law is "simple" is your first mistake. Don't forget - without an accountant willing to take responsibility, they'll go after you. Do you think you could handle an in-depth investigation by the Polish Urzad Skarbowy, particularly if you did the accounts yourself without much knowledge of Polish tax law?
I know one lawyer for the Urzad Skarbowy, and in her words, anyone attempting to do the paperwork themselves for a limited liability company without using accountancy services is setting themselves up for an investigation. It attracts attention in the wrong way - think from their perspective. A foreigner trying to do accounts himself without knowledge of Polish accountancy law is bound to make mistakes, not least because the law is different to their home country.
Given the international nature of my work, I suspect most of the time they will actually be paying me rather than the other way round.
There is absolutely no way that they are going to be paying you money on a regular basis without an investigation being launched.
Most of my invoices will be non VATable as most of my revenues will be generated outside of the EU and very little if any is expected from directly within Poland.
This will also arouse suspicion. Remember, Poland hasn't really been used for such businesses - the tax law isn't business friendly.
I don't see what is so complex about that to require a tax accountant.
Listen to what people are telling you. Trying to assume that it's "simple" in a country like Poland is utter madness. Remember, many of these tax laws were more or less written from scratch 20 years ago - there isn't years of tradition and experience to fall back on, nor is there a culture of the taxman working with the taxpayer to get it right.
all my overheads are outside Poland
All? That would arouse considerable suspicion if the director's address was in Poland...
I'm no accounting genius (and I steered well clear of doing my own accounts for a sole trader despite knowing more or less how to put basic accounts together) - but given the amount of questions you've asked on here, don't you think a good accountant would be mandatory for someone with such little knowledge of Poland?
(PS : a free hint - most English resources about Polish tax law are nonsense)