Tax-free income is any type of income that is not subject to income tax. This can include certain types of investments, such as municipal bonds, which are issued by state or local governments and are generally not subject to federal income tax.

Additionally, certain types of income may be exempt from taxes under certain conditions, such as:

• Gift and inheritance: usually not subject to income tax
• Certain types of investments and savings, for example, contributions to pension plans
• Certain social security and welfare benefits
• Some types of business income, such as those earned by certain non-profit organizations
• Income from foreign sources if certain conditions are met.

It is important to note that tax laws and exemptions can vary by country and by state within a country, so it's essential to consult with a tax professional or consult the relevant tax laws in your jurisdiction to determine what types of income may be tax-free.