<prompt> Human: First post in this forum, but long time learner. I hope this topic goes in this sub if not please kindly let me know.Heres some context: My friend well call her K recently finalized her divorced and she obtained 100 custody of their 2 kids 6yo and 4yo , both kids have lived with her for the past 2 years or so , since her and the now ex-husband split up. The divorce and parental rights was smooth and no complications on either side. K as well as her Ex husband are both immigrants and the two kids are US Citizens.There are two situations were things get complicated and need advice in order to help my friend K:Situation 1: The kids Dad has been claiming both kids in his taxes they file separately since the first kid was born. This 2017 was the first year my friend K filed her own taxes and claimed both kids and she of course got more money than she expected, when the kids Dad noticed she had done this , he got very upset and stopped talkingseeing the kids for a couple of weeks. My friend K feels her EX might attempt to file taxes before her beginning of next year.Situation 2: My friend K and her kids will be going back to her country for and indefinite time. after she receives the tax return for TY-2017 and can afford the tickets. Questions:1 - How can my friend K prevent her EX-husband to claim both kids in his taxes, not only this coming year but every year afterwards?2 How can the kids SSN be protected so no one uses it to get work or to obtain credit? Please let me know if I can provide any more information.Thanks!  <response>: the benefit goes to the parent who has the child more than 50 of the time. unless there is a written agreement to the contrary.So assuming that is her. he if rushes to file and puts them as a dependent, the IRS will reject an E-file from the mother, she should file a paper form and things will proceed as per normal. some time later a year or so both parties will get a letter asking them to amend their return to correct the issue. If neither party amends, then both parties will get a followup asking for proof of their claim of the dependent. Of course she will be able to provide it, and he will not.I would suggest she inform him of this fact, as a kindness so he can avoid the hassle and complication, as it is really no skin off her nose to do this, its only going to create a mess for him. 