Some things to check are:
- Is the income type or amount different?
- Are your state taxes withheld different?
- Did you have credits last year, that you don't qualify for this year?
- Did your filing status change?
- Did your dependents change?
It might be a good idea to review your entries to make sure that's all accurate. Also, just doing a side-by-side comparison over the prior year may help you see what's different.