It it my opinion that getting a tax deduction for a charitable act one did in that tax year is wrong because it gives a specific, unnecessary reward for one’s charity, making it more of an act of reciprocal benevolence than true, unmerited and unselfish charity. Just because an act is charitably beneficial or good in itself does not mean that everything else attached to it is good, or that the intentions of the individual are necessarily pure. Again, I am not accusing anyone of anything. However, assuming that tax deductions from charitable works is not mandatory (as in, one could choose not to get a tax deduction from their charity), I think that a truly charitable act, in the interest of doing it purely for its own sake and not for personal reward, should not involve tax deductions.
I am somewhat ignorant on this - if the government does tax deductions on charity whether the individual wants it or not, or if it does it in, as you say, a non-itemized way, lumping it in with other tax deductions whether the individual likes it or not, then one cannot be liable for it. But if you specifically allow a tax deduction for your charity, then I think it has the potential to corrupt that charitable act into a desire for reward, at least partially. Again, this is my opinion. I’m not stating it as a definitive matter of morals or as a representation of official Church teaching. As always, if there is a specific Church teaching about tax deductions, I am entirely willing to change my opinions to accord with them. God bless.