At least in the UK, these two words have entirely different meanings when applied to tax. Tax evasion is not paying tax which is due. Tax avoidance is arranging your activities to reduce or minimise the taxes which are due.
When I check the box to count my daughter as a dependent, I am "avoiding" taxes. When a multi-national corporation inverts their company to Canada, they are "avoiding" taxes. So long as all of the above are within the rules, neither act is immoral.
You still end up with less money than had you not given to charity, and it's MEANT to work this way. It's a very different kettle of fish to exploiting tax loop holes.
And penalizes the government. I'm happy giving my own money to Music For Rich Old White Dudes, but I don't think it's moral for me to take money away from the general taxation pool for that.
I would argue that it's not illegal but if you're defense of an action is "It's not technically illegal", there's a good chance it's immoral.
The result of that is that I pay less in taxes than if I had lied.
Are you honestly suggesting that lying is morally superior?
You do realize that setting up entities expressly for the purpose of avoiding tax is illegal in most jurisdictions right?[1-3] The absence of aggressive enforcement doesn't obviate the illegality of the actions.
In your scenario, those humble multinational corporations who are so beholden to the truth have to tell the tax authorities that the dozens of subsidiaries all have actual and legitimate business purposes and that they weren't set up merely to avoid taxes. I mean, it really is obvious why Apple transferred most of their IP to an Irish subsidiary for non-tax reasons, isn't it?
[1] - https://www.gov.uk/government/publications/tax-avoidance-gen...
[2] - http://assets.cambridge.org/97805218/87779/excerpt/978052188...
[3] - http://www.insurancejournal.com/news/national/2012/05/15/247...
I don't believe that is true. There are ~200 countries in the world. The UK, a pretty advanced nation when it comes to tax, did not implement general anti-avoidance legislation until last year. (See your footnote [1] for the exact date.)
Moreover, this anti-avoidance legislation is specifically targeted at what HMRC calls 'abusive avoidance'. It is not targeted at all avoidance.