There is no minimum amount below which interest and dividends do not need to be reported, except that amounts below $0.50 can be rounded to zero if you use whole dollar reporting. Itu2019s only if your total income is low enough that you do not have to file that you can avoid reporting.As a practical matter, if you receive a 1099-DIV or 1099-INT or other form from a financial institution, then the IRS will check that you have reported the income on your tax return. If you did not receive such a form, then itu2019s up to your personal honesty.If you received a small amount of interest from an informal loan no one reported to the IRS, or perhaps a small foreign transaction, itu2019s unlikely the IRS would find out. But if it did, say in a tax audit or if someone turned you in for the reward (ex spouses and lovers are common informants, also the people who paid you the money), you would be liable for taxes plus interest and penaltiesu2014which in theory could include criminal penalties but likely wouldnu2019t for small amounts that you could have plausibly forgotten.But even without a form, you do owe taxes on the money. Lots of people fail to report this kind of thing, but it is cheating not to do so.