For reporting tax purposes, if a company does not send a 1099, I still report it as income, but what do I provide as proof of that income? Is there an official document of some sort that I need to create to attach?
“Every cent of earned income through side jobs, gambling, prize money, and so forth must be documented. You may use your bank statements or check stubs to document the income. The IRS does not request this documentation when you file your taxes at the beginning of the year, but you need to keep it in case you are audited.”
So nothing needs to be attached but you need to keep the proof of the income via check stubs and/or bank statements as stated above.
Print out the paypal statements... check stubs... bank statements showing direct deposit. I am in the middle of an IRS audit for 2015 right now, but they only want my mileage records and receipts. They did not request any income information (yet).