Brownfields Redevelopment Tax Incentive Reauthorization Act of 2018 This bill amends the Internal Revenue Code to extend through 2021 the election to expense (i.e., deduct in the current taxable year) environmental remediation costs (i.e., costs for the abatement or control of hazardous substances at a qualified contaminated site). The bill applies to expenditures paid or incurred after December 31, 2017.