This tax cost must be taken into consideration when forecasting cash needs. There is no standard record-keeping system prescribed by the Internal Revenue Service (IRS). An individual taxpayer whose primary source of income is salary or wages will probably choose a more informal record-keeping method that consists of nothing more than a collection of papers (called source documents by accountants) representing the receipt of income and the payment of expenses during that tax year. Any person keeping records so informally risks the loss of tax deductions otherwise allowed, due to failure to produce an important paper that evidences the right to a deduction.