It doesn't know your info even if when your return is complete. if they're doing their own return the parents must complete theirs first so the necessary info can be entered on the kids form 8615. with multiple kids filing, this is not a Turbotax strong point since the info must be enter manually rather than imported (pro software handles this but then there are the pros costs of doing all the returns)
TurboTax instructions
Enter parents' taxable income from Form 1040 or 1040-NR, line 15. If the parent filed Form 2555 or 2555-EZ, enter the amount from line 3 of the parent's Foreign Earned Income Tax Worksheet, instead of the parent's taxable income. If the line 6 amount is not known at the time of filing, the child can get an automatic 6-month extension of time to file. For details, see Form 4868, Application for Automatic Extension of Time To File U.S. Individual Income Tax Return.
Other Children Filing Form 8615 - Schedule D Smart Worksheet
The other child's name is calculated to this table when there has been an entry in the total net capital gain and net capital gain columns on the Other Children Filing Form 8615 - Line 5 Smart Worksheet. This worksheet is used when the child's return has a Qualified Dividend Capital Gain Tax Worksheet or Schedule D Tax Worksheet.
Other Children Filing Form 8615 - Schedule D Line 15:
If the child's return only has the Qualified Dividends and Capital Gain Tax Worksheet, enter the amount of long term gain from line 3 of the worksheet.
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note that under certain conditions the parents can report the kids income on their return using form 8814.
this can only be done if
1) the child's only income is from interest, dividends, and capital gain distributions (not if the child had security sales)
2) the child's gross income for the year is under $12,500
3)there were no 2022 overpayments on the child's return applied to 2023
4) no estimates or withholding for the child
5) the child was under 19 or under 24 if a full-time student
6) the child is required to file for 2023 and does not file a joint return if married.
