I paid taxes in 2018 for an error on a tax return in 2015. Can I enter that as taxes paid in 2018

[MichaelMc · Accepted solution]

Yes.

If you paid state income tax in 2018, or state and local taxes such as property tax, whether regularly assessed or because of an error in a prior year, those taxes are deductible in the year actually paid.

Please be aware that, as a result of the Tax Cuts and Jobs Act of 2017, the state, local, property, and sales tax (SALT) deduction is capped at $10,000 ($5,000 if married filing separately).