Plenty of factors affect differing results each year. Double check the forms themselves to see if it makes sense... I've been using TT for more than a dozen years and yet I still go back and read each line of the forms it fills out to see if either of us missed something. (Saving me a grand this year because I jumped through the interview process too quickly!)
And never forget, the big return you are looking for is an interest free loan you gave the government. Fiscal prudence should motivate you be as close to ZERO as possible when you file.
