If the CD is in a tax-deferred or tax-free account, such as an IRA or Roth IRA, interest on the CD is not currently taxed; the rollover of the CD when it matures is not a taxable event. If the CD is in a taxable account, interest is taxable, but again rolling over the proceeds when the CD matures is not a taxable event.
A tax year of less than 12 months. May occur with the startup of a business or change in accounting method.