I need to create a new packing slip to correct the cancellation in a way that aligns the dates correctly: the transaction date for the project should be in 2024, and the voucher date should be in 2025.

Hi,
I think the two dates come from the closed period: the cancellation reversed the project transaction on its original 2024 date, but the voucher couldn't post into the closed 2024 period, so it landed in the first open date (2025).
I don't think a new packing slip will give you a 2024 transaction date with a 2025 voucher date, since both normally follow the packing slip date. Going from general knowledge, so please check with your finance team, here are some options:
1. Temporarily reopen the 2024 period in the ledger calendar, post the correction dated 2024, then close it again. This changes closed-year numbers, so it needs finance/audit approval.
2. Post the new packing slip with a 2025 date so both the transaction and voucher are in 2025, and document the link to the 2024 original. For a closed year this is usually the cleaner approach.
3. Check whether a project transaction adjustment can change the date. I'm not sure what it allows on posted transactions, so test it first.
Is the date split actually causing a problem for you, or just unexpected? Some teams accept it when a cancellation crosses a closed period.
Hope this helps!
Thanks.