You constructively receive income when it is credited to your account or made available to you. You do not need to have physical possession of it. For example, you are considered to receive interest, dividends, or other earnings on any deposit or account in a bank, savings and loan, or similar financial institution, or interest on life insurance policy dividends left to accumulate, when they are credited to your account and subject to your withdrawal. This is true even if they are not yet entered in your passbook. If you use an accrual method, you report your interest income when you earn it, whether or not you have received it.
Interest is earned over the term of the debt instrument.
If, in the previous example, you use an accrual method, you must include the interest in your income as you earn it. Interest on coupon bonds is taxable in the year the coupon becomes due and payable. It does not matter when you mail the coupon for payment.