Offer your thoughts or opinion on the input financial query or topic using your financial background.

Do I have to explain the source of *all* income on my taxes?
As a gift, the responsibility lays with the giver to file a 709 with their taxes for gifting to a single entity (barring certain exclusions) an amount over $14,000 within the (2017) tax year. https://www.irs.gov/pub/irs-pdf/i709.pdf If this person is a foreign entity from outside the country, you might need to provide in your tax filing a form 3520 https://www.irs.gov/businesses/gifts-from-foreign-person The reporting limits are: more than $100,000 from a foreign estate or non-resident alien, or more than $15,102 from a foreign company. If you don't know who/where the money came from i.e. cash, it would be considered found money and fall under income (not a gift).