Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

When transferring money between two parties, under what circumstances is it considered taxable income?
A loan is not a taxable income. Neither is a gift. Loans are repaid with interest. The interest is taxable income to the lender, and may or may not be deductible to the borrower, depending on how the loan proceeds were used. Gifts are taxable to the donor (the person giving the gift) under the gift tax, they're not a taxable income to the recipient. Some gifts are exempt or excluded from gift tax (there's the annual exemption limit, lifetime exclusion which is correlated to the estate tax, various specific purpose gifts or transfers between spouses are exempt in general).  If you trade for something of equal value, is that considered income? Yes. Sale proceeds are taxable income, however your basis in the item sold is deductible from it. If you borrow a small amount of money for a short time, is that considered income? See above. Loan proceeds are not income. does the friend have to pay taxes when they get back their $10? No, repayment of the loan is not taxable income. Interest on it is. Do you have to pay taxes if you are paid back in a different format than originally paid? Form of payment doesn't matter. Barter trade doesn't affect the tax liability. The friend sold you lunches and you paid for them. The friend can deduct the cost of the lunches from the proceeds. What's left - is taxable income. Everything is translated to the functional currency at the fair market value at the time of the trade. you are required to pay taxes on the gross amount Very rarely taxes apply to gross income. Definitely not the US Federal Income taxes for individuals. An example of an exception would be the California LLC taxes. The State of California taxes LLCs under its jurisdiction on gross proceeds, regardless of the actual net income. This is very uncommon. However, the IRC (the US Federal Tax Code) is basically "everything is taxable except what's not", and the cost of generating income is one of the "what's not". That is why you can deduct the basis of the asset from your gross proceeds when you sell stuff and only pay taxes on the net difference.