There were many changes to the tax forms and deductions.
Check this FAQ
https://ttlc.intuit.com/questions/1901008-why-did-my-refund-go-down-compared-to-last-year-s Mainly because they reduced the withholding tables. So they didn't take out as much withholding as before. So you would get more back in your checks each week or month. It's been all over the news. More people are owing this year or getting smaller refunds.
