On the evening of December 15, 2017, Congress released the Conference Report on its Tax Cuts and Jobs Act (the "Act"). Among the provisions is one that prevents individuals from claiming an itemized deduction in 2017 for prepaying their 2018 state income tax in order to avoid a new $10,000 limitation on deducting such taxes. Just one day earlier, the Massachusetts Department of Revenue ("DOR") had announced a means for individual taxpayers to make such prepayments.

Under the Act, individual taxpayers may claim an itemized deduction of up to $10,000 ($5,000 for a married taxpayer filing a separate return) for their aggregate state and local property, and either income or sales, tax paid or accrued in taxable years beginning in 2018 outside a trade or business. The conference report also provides that, in the case of amounts paid in 2017 for state or local income tax imposed for 2018, the payment will be treated as paid on the last day of 2018 for purposes of the dollar limitation. "Thus, under the provision, an individual may not claim an itemized deduction in 2017 on a pre-payment of income tax for a future taxable year in order to avoid the dollar limitation applicable for taxable years beginning after 2017."

One day earlier, on December 14, DOR had announced a method for individual taxpayers to make estimated tax payments for 2018 using MassTaxConnect, which is DOR’s online site for filing and paying taxes in the Commonwealth. See Making 2018 Estimated Payments for Individual Taxpayers on MassTaxConnect. Under the Act, there is little incentive to do so.