1) Free of duties 2) Like churches, usually 3) Like interest on some bonds 4) Like many charities 5) Like some municipal bonds 
Referring to income which is not liable for tax in the hands of the recipient. Referring to a fund which does not incur tax on its income, by virtue of its beneficiaries being a specialised class of persons, e.g. a charitable organisation.
Refers to income or property which is not subject to tax. Interest on Municipal bond is not subject to federal income tax. Similarly, interest on a treasury bond is not subject to state or local income taxes. 
[adj] - (of goods or funds) not taxed
tax-free adjective (of goods or funds) not taxed; `tax-exempt bonds`; `an untaxed expense account`
A condition of the law in which an organization or people in some kinds of work do not have to pay taxes which regular citizens or businesses must pay. Religious organizations are often tax-exempt.