When you use online TurboTax, you get one return per fee, so you and each child will need your own accounts and your own user ID's. You can use the same email if you want. You will be able to transfer your 2024 data in to the 2025 online software. You do that transfer at the very beginning before you enter any new 2025 data.
Online for 2025 will be available in early to mid-December.
https://ttlc.intuit.com/community/using-turbotax/help/how-do-i-start-another-return-in-turbotax-onli...
https://ttlc.intuit.com/turbotax-support/en-us/help-article/import-export-data-files/transfer-last-y...
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