Hi,
With the given information in your question and looking back at similar questions asked, if your rental business began on 2nd October 2023, we would not expect a Self-Assessment Tax Return to be submitted until after 6th April 2024 when the current tax year ends.
With this in mind, you would then check the Self-Assessment criteria to determine if a Tax Return is necessary for the first year of rental found here:
Check if you need to send a Self Assessment tax return.
In terms of any penalties, I would not expect that any penalties would be applied to either record if registration is completed indicating that rental income commenced in the current tax year, 2023/2024.
Thank you.