Multiple issues:

1) He may be able to claim his own child but, unless that child lives with him, he can not claim Head of Household.

2) Unrelated persons (you and your child) can only be claimed as dependents if you live lived with him for the entire year. May through December does not cut it.

3) Unrelated persons (your child) can not qualify for the Earned Income Tax Credit or the Child Tax Credit.

He needs to pay the money back.

Note: All this changes when you get married. Step children are treated exactly like biological and adopted children. However, none of this happens until you say "I do".

Does his own son live with him? If not, he doesn't qualify your fiance as head of household. You and your son aren't related to him, so you don't either. And anyway for HofH he'd have to pay OVER half, not split 50/50 - that's not OVER half - so he is definitely not HofH.. If you made $3900 or more, he can't claim you OR your son. In any case he can't claim a child tax credit or EIC for your son.

What did he do wrong?

1. He claimed you and your son as dependents when you did not live in his home for ALL of 2014. That kills the exemptions. There are other tests that must be met, but since this one fails the others are irrelevant. (Even if you did live in his home for all of 2014, neither nor your son are qualifying persons for HoH filing status.)

2. You have not provided enough information on claiming his own son. Unless his son lived in his home for more than half of 2014, he cannot claim him or file as HoH.

3. Even if his son did live with him for more than half of 2014, to file as HoH he MUST have paid MORE than half of the cost of maintaining the home. An even split does NOT qualify.

4. Basically he made up his own rules as he went along instead of reading IRS Pub 501 https://www.irs.gov/pub/irs-pdf/p501.pdf and following the IRS' rules.

He needs to review IRS Pub 501 and see if he can claim his own son. If he can he should prepare an amended return using Form 1040-X to adjust his tax liability and establish what he actually owes. If he has PROOF that he paid more than half of the cost of maintaining the ENTIRE home he can file as HoH. If he can claim his son, he MIGHT qualify for the EIC unless the IRS decides to play hardball if he claimed the EIC using your son.

if you only lived with him since May 2015 (or even just since May 2014) and he is being audited for 2014, he is going to lose and wind up owing taxes, penalty and interest - he can only claim you if you lived together 365 days of the year - he violated the rules

Your fiance cannot claim you or your child because you and your child did not live with him the entire year. He cannot use you or your child to qualify for Head of Household because neither you nor your child are related to him.

If your fiance claimed his own child, and that child lived with him for more than six months, and your fiance provided over half of the household support, then he may qualify to file as Head of Household. If this is the case, he needs to provide documentation the IRS finds convincing. From your information, it sounds like he did not provide over half of the household support.

U didn't read the instructions for many of those deductions.

Local libraries have plenty of books on how to figure out what you qualify for and what u don't.

Start saving, selling things, 2nd jobs to cover the tax bills.

living with him since May is not enough it has to be the ENTIRE year for you and your son

and you do not qualify him as head of household nor does your son since he is not directly related to your b/f

if his own son did not live with him he does not qualify for head of household on that basis either

if your b/f prepared his own taxes he need to read up first on what he is eligible to claim, the publication 17 at www.irs.gov will be priceless to him

if he let someone else prepare this return and he paid for it, he needs his head examined, and definitely DO NOT use this guy again

Did your boyfriend's son live with your boyfriend for 180 nights during the year? If not, your boyfriend does not qualify to claim the child.

For your boyfriend to claim unrelated individuals as dependents, you had to live with him for the full year. You did not, so you are not tax dependents.

He can't claim you if you didn't live with him all year. Ditto for your kid. Even if he could claim you and child, he cannot claim HoH based on you.

He has to pay MORE than half the bills, half isn't enough. "We do our thing he does his" doesn't cut it.

He claimed things he wasn't allowed to is what he did wrong.

He should be. You and your son are NOT his relatives - so he can

NOT claim both of you.