I feel that she has all of the years available for just the reason you said - taxes. She would have had to have filed, unless, like here in the US, she got some sort of extension, by which you would still need to file an estimate of tax owed (if you owed). Certainly, 2020 would have been taken care of by now, as would 2021. She is lying.
What I believe we are seeing from Stephanie at the moment - time will tell if something more nefarious is really going on - is the fact that she sold these patrons a bill of goods. She dumped all of the money in one account, whether it was YouTube money or Patreon money, then she spent it like it was all her money, without any thought as to how she should be accountable to this "association" she told Patrons they'd all be a part of. Now that she's rolling in cash, got her Patrons "hooked", she's changed the rules, using Patreon money to fund her renovations, but not giving Patrons a first shot at seeing them, letting them instead be shown to viewers on the Channel 4 show first. She has to know how this gives Patrons pause.......and I think she's more afraid of her Patrons - AS SHE SHOULD BE! - than she is any government or legal entity at this point. You can see the fear all over her face and in her body language because she knows she has royally f*cked up - people will be angry enough to pull their Patreon account, and then the money goes away.
Someone said earlier if she had just come clean, confessed that she didn't do this correctly, it could have been straightened out. I agree with that. But to continue this farce, blaming accountants or just stonewalling Patrons, makes her not only more hated by those of us who see right through it, but can also begin to cause those legal issues that I don't think she would have had if she'd just confessed the original blunder.