[quote=flu]
My taxable income between 2018 versus 2017 is about the same, but the total federal taxes I’m paying this year is about $17k less than last year, and my effective tax rate dropped by 5%.[/quote]

You hinted your AGI around $340K. That is a real sweet spot with the new tax law. Assuming 24K standrad deduction, txable income is 316K. It used be 33% tax bracket for income above 233K in 2017, now income above 157.5K and below 315K are only taxed at 24%. That is 9% drop in tax rate. For AMT tax payers the marginal rate was 32.5% or 35% corresponding 26% or 28% AMT rate. Every extra dollar of income also reduces AMT exemption by 25 cents, so that is how 32.5% come from: 1.25 x 26% = 32.5%

Child credit $2k for every child under age of 17. 3 kids can get 6K credit. Old law phased out child credit starting at 110K, now full credit if AGI < $400K My AGI in 2018 is 8K less than 2017 due to the family leave time taken, but total tax is $9k less. Adjusted for income difference to assume AGI are the same for the 2 years, my tax would be 7K less. Main difference maker for me: Lower marginal rate of 24% from previous 32.5% AMT rate. No more AMT.