sentences:  The taxpayer must choose a tax accounting method using the taxpayer's financial accounting method as a reference point.Proper accounting methods are described in section 446(c)(1) to (4) which permits cash, accrual, and other methods approved by the Internal Revenue Service (IRS) including combinations.After choosing a tax accounting method, under section 446(b) the IRS has wide discretion to re-compute the taxable income of the taxpayer by changing the accounting method to be used by the taxpayer in order to clearly reflect the taxpayer's income.