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Explanation: I know that you have awarded an answer, but I just wanted to contribute my "two cents" worth.
In a formal accounting or tax document, the term "tax-exempt" would probably be more appropriate. There is also a subtle difference in meaning. In the case of a donation, for instance, the donation itself would probably not be taxed in any instance. There is not typically a tax placed on the act of donating. So, calling a donation "tax-free" probably does does not convey much information. However, in the tax system of the United States and perhaps other countries, a charitable donation may be subtracted from the taxpayer's income when calculating tax due. This creates a "tax-exempt" portion of income. In this instance, "tax-exempt" is much more meaningful than "tax-free".
I hope I haven't created confusion rather than shed light on a matter which you had already decided.
One more note: whether you use "tax-free" or "tax-exempt", please be sure to include the hyphen. I admit this is a fine point of English orthography but it should probably not be left unsaid.
MBA, experience (on the "giving" end) with the United States taxation system 18 years as professional translator
Alan Lambson Local time: 23:16 Native speaker of: English PRO pts in pair: 114
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