My husband moved out in the middle of December can I file taxes separate and can I claim the 3 kids?

You can file under the category "married filing separately". You should file your taxes immediately. If you file electronically before your soon to be ex, then he will be precluded from filing electronically. If he does claim the kids, he will have to paper file and the IRS will investigate as to who has the right to claim them. As he left the kids with you, most likely the IRS would decide in your favor. As an aside, you should also file a petition for custody, parenting time and support to keep the kids with you and get your husband paying child support immediately. If you have been a stay at home mom and the kids are small, you can also request alimony for a period of time, including time to attend school to seek a higher paying employment.

You should get an attorney and potentially file for divorce, seeking an ex parte order for him to have to maintain the status quo as to marital obligations and pay child support. Until I know more the circumstances I do not know whether or not I would recommend your filing separately. If there becomes a issue regarding who actually provided the support for the children, and encourage any deductible expenses, from the thanks which you have presented you would not be a party who would be awarded them. Get advice before you do anything which is a irreversible.

You can file separate. If you provided a majority of the support for the children, you can claim them as your dependents.

Yes, you may file "Married Filing Separately" , and claim all three children as Dependents.