No it's no excuse, but it may go a long way to explain why he's been so adamant about his innocence. Obviously his lack of academic skills haven't held him back in his ability to get the best out of players and create good football playing 'teams'.
I think, whether we're literate or not, that we've all done what he's claiming. You see a set of T&C's and who bothers reading them - you just tick the box that says you have....you get a text return and you fill it out without fully understanding what you're supposed to fill oyt and which bits you're not - who reads the 'explanatory' booklet that comes with it? IMHO it's not always about literacy - even being literate doesn't mean that 'form' speak doesn't throw most people. I bet 'arry gets his tax return completed by his accountant with a couple of pencil marks to tell 'arry where to sign and date. Obviously, he should have declared all his earning to the accountant anyway. But so far 'arry seems adamant that they all knew about his off shore accounts - so maybe his mistake was to 'assume'. On the other had he may simply be a devious git and knew he was fiddling all along (but if that is the case I'm a bit lost as to why he has gone to court, as the evidence of the offshore account alone looks damming enough). Who knows?