It could make several differences, you lose the personal exemption for $4050 first of all.
There are many, many reasons this could be. Could be income, with
holding, EIC, Child Tax credit, itemized deductions, business income/loss,
interest income, exemptions, dependents, education, additional taxes,
mortgage....
I would first print your 2016 and 2017
returns and compare them line by line.
This will help you determine what has changed, if there are any
discrepancies/items you missed or if you need to change any of the information
you entered into TurboTax.
There are several factors that go in to determining the taxes you
owe.
If your income increased,
which might have put you in a higher tax bracket, it could have reduced or
eliminated some deductions or credits and the tax laws changing year to year
will determine the amount of taxes that need to be paid as well.
Also, you may have paid in a
lesser percentage of Federal withholding per dollar than you did last year.
If your income decreased, that
sometimes can reduce your refund due to you not having enough earned income to
receive the deductions or credits you did before.
From <https://ttlc.intuit.com/questions/4188720-can-you-explain-to-me-why-my-return-went-down-so-low>
Tax refunds
(both federal and state) are a function of your taxable income, tax
credits (if any), deductions, and taxes withheld. As well as the tax bracket
that you are in. From the information you provided, there is no way for Turbo
Tax to determine why your refund is smaller this year. We would have to examine
prior year as well as current year to give you anything more than a guess
as to why.
From <https://ttlc.intuit.com/questions/3962032-why-is-my-refund-so-low>
From
<https://ttlc.intuit.com/questions/4208942-why-is-my-tax-return-this-year-so-small-last-year-i-get-ba...>
