I'm filing 2015 taxes. I can't remember if my dependent's father claimed them that year. Will there be a problem if I claim them and it turns out that he did also?

[mflo2320-jj]

He can't remember either, but i know there was one year where it was advised by the tax preparer that their father should claim them. 

[Anonymous]

yes. there will be a problem if both claimed.  but a better question is are you due a refund? the time limit for filing for a refund for 2015 expired on 4/15/2019 unless the return was extended. then you got til 10/15/2019.  if you have until 10/15 then the question becomes    

could he have claimed you (but is not required to) for 2015

he could if 

you were under 19 or under 24 and a full time student

he provided over 1/2 your support

you didn't file a joint return showing a tax liability

if the answer to all 3 is yes, you should not be claiming yourself on the 2015 return . check the box someone else can claim you.