4 Optional standard deduction. An optional standard deduction is provided on the Iowa

individual income tax return for both residents and nonresidents. In the case of married taxpayers filing separate returns or separately on the combined return, if one spouse takes the optional standard deduction, the other spouse must also take the optional standard deduction. The standard deduction claimed by the taxpayer may not exceed the taxpayer’s income before the standard deduction. A taxpayer has the option of itemizing deductions or of using the optional standard deduction on the Iowa return, regardless of the deduction method used on the federal return. For tax years beginning on or after January 1, 1990, the optional standard deduction amounts are indexed or increased for inflation by the cumulative standard deduction factor. The cumulative standard deduction factor is described in rule 701—300.12(422). This rule is intended to implement Iowa Code sections 422.4 and 422.9. [Editorial change: IAC Supplement 11/2/22; Editorial change: IAC Supplement 10/18/23]