If your grandchild has been living with you since January of 2024, then you should be able to claim her as your dependent. Depending on her age (and your own income) you may get child-related credits such as the child tax credit, earned income credit, or the childcare credit. And you may be able to file as Head of Household, which will make less of your income taxable.
Am I Head of Household?
https://ttlc.intuit.com/questions/1894553-do-i-qualify-for-head-of-household
https://ttlc.intuit.com/questions/2900097-what-is-a-qualifying-person-for-head-of-household
If you qualify as Head of Household, when you enter your marital status (single or married filing separately) into MyInfo, and then enter your qualifying dependent, TurboTax will offer HOH as your filing status.
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
