A notorized letter has no particular custody rights significance.
The court order of custody is the controlling document. Without some kind of transfer of custody there simply is no such transfer.
Giving temporary custody by a notorized letter is not authorized by the court, right?
Agreed, a notarized letter has no particular child custody significance, except that it is evidence of intent.
If there is a custody order, that controls. If there is no custody order, the biological parents share custody (this is information gleaned from limited facts). If there is no custody order for this child, it may be wise to seek one.
Assuming that the child is not in danger, be aware that sudden changes in a child's living environment and changing their primary caretaker can be traumatic for the child. I suggest contacting an attorney with experience in custody issues to develop a smooth transition plan for the child.
If nothing has been filed in court, does this mean that this is a biological parent who was never married? If there was a divorce, there would be custody papers. If someone went to court for child support there would be custody papers.
Here's the rub in your situation: where has the child been living? If brought to the court's attention, the court will want the child to have stability, and to stay temporarily with the person who has been providing this child a home, until the Court can hear what's in the best interests of the child. Preference is given to the child's current custodian, even if that custody has not been recorded with the court. Now, if the current residential custodian is harming the child, then the natural parent has grounds to go back and get the child, as being in an abusive home is not in the child's best interests.
If no one is willing or wants to go to court, yes, you can just go get the child. But, be aware that the above problem could arise.
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