Possibly, I've also seen it suggested that he wants to keep his level of tithing covered up - seeing he's given millions to the Mormon Church might remind people of where his beliefs lie and put off some on the religious right from voting (or on one of the more out there suggestions, that he's worried the Mormons would see he's not being paying as much as he should. If it is something like that then it is a bit tough for him - it is a private matter, in my view, with things like that.

As for the off shore money, I don't see why people shouldn't know how much he squirrels away abroad to avoid taxes in the US - if he thinks avoiding paying millions in tax and depositing money that he could have invested in US firms, which would have a knock on benefit for the US economy, is the right thing to do then he should say so, not hide it. He's offered up tax plans as part of the election platform, so it seems perfectly fair and reasonable to me to know what his real views on tax are.



The flip side though is that if it came out that the IRS are going through his taxes with a fine tooth comb then it would be damaging to the IRS and Obama - the fact he is running for President might well make them very wary of going after him. His tax returns are also likely to be massively complex - hard to justify trawling through them in detail, given they don't even know what they are looking for.
Who knows, maybe he has struck a deal with the IRS to pay of back taxes he owed already and doesn't want it to come out that he was under paying (either deliberately or in error)?