The short answer

What it reportsOriginal issue discount; market discount subject to an election under section 1278(b). OID on U.S. Treasury obligations and tax-exempt OID are also reported on this form. Stated interest (other than stated interest that is OID) may be reported on this form.
Amounts to report$10 or more
To the recipientJanuary 31
To the IRS, on paperFebruary 28
To the IRS, electronicallyMarch 31

If one arrives

Taxable as it accrues, in the year it accrues, even though no cash arrived.

The form is how a payer tells the IRS what it paid. Its absence is not permission — income you received is reportable whether or not a form covers it, and a threshold decides only who must file, never what you owe.

This page is for educational purposes only and does not constitute tax, legal, or financial advice. It covers United States federal reporting. Consult a qualified tax professional about your situation.

Official sources