In a situation such as yours, where someone else has already filed their tax return claiming your foster child, the IRS may give them the deduction since their return was processed first. The IRS will not let you Efile your tax return since someone else has used your social security number, so the only option would be for you to paper-file your tax return. To do this, you would select Paper-File instead of Efile when you are in the File stage of completing your return. Then print, sign, date and mail your tax return by April 18, 2017. The IRS will probably investigate who really should be getting the deduction. At that point, they will make a decision based on the criteria below, and the taxpayer who incorrectly claimed the dependent will be assessed any additional taxes and penalties, and required to file an amended return. If you would like to call the IRS and report this, their number is 1 (800) 829-1040, but they probably will tell you exactly what I have told you.
A parent may claim their child if they meet either the qualifying child or qualifying relative test as outlined below:
Qualifying Child
These 5 tests (all of them), will qualify a child as a dependent:
Qualifying Relative
These 4 tests (all of them) will qualify a relative as a dependent:
If I filed my biological children on my return from getting them back and had them for 5months august-December 2020 and the Forster parents try to file from January to July ..what will happen ..will I be able to still file them
No. You cannot claim them because they lived with you less than half the year. The foster parents can claim them because they did live with them for more than half the year.