Net income is the amount earned by a company after subtracting out the expenses incurred, including depreciation and taxes. Average total assets in the denominator of the return on assets formula is found on a company's balance sheet.The average of total assets should be used based on the period being evaluated.et income is the amount earned by a company after subtracting out the expenses incurred, including depreciation and taxes. Average total assets in the denominator of the return on assets formula is found on a company's balance sheet. The average of total assets should be used based on the period being evaluated.