There are so many changes in the new tax law that it's very hard to make a direct comparison between 2017 and 2018. Also as a result of the new law, the withholding calculations that employers use were changed early in 2018, so your withholding might have been different. You can try to compare the major amounts in your 2017 and 2018 tax returns to see where the significant differences are, but you might not be able to go line by line. Look at total income, Adjusted Gross Income (AGI), taxable income, total tax, and total payments (or amount of withholding). When you see where the difference is, you can narrow it down from there.
