You don't have a choice about whose income it is. The income belongs to the person whose name and Social Security number are shown as the recipient on the 1099-MISC. That person has to report it on his or her tax return. And you have to report the full $700. You can then report the expenses on the same tax return.
If the income is the child's, and the net income after subtracting expenses is less than $400, and that is the child's only income, then technically the child does not have to file, as SusanY1 said. However, I would recommend filing the return anyway. The IRS doesn't know about the expenses unless you file the tax return. If they see $700 on a 1099-MISC and it hasn't been reported, they will assume that there are no expenses and it is all income. I think it's virtually certain that the child will get a notice from the IRS about unreported income. And it won't just be an inquiry. It will say that the tax return has to be filed, or it will be a bill for unpaid self-employment tax plus penalties and interest. Filing the tax return now will be a lot less hassle than dealing with an IRS notice a couple of years from now.
I don't know what you're referring to by "under pub 929." IRS Publication 929 was discontinued two years ago. There is no Publication 929 for 2024 tax returns.
