Hi KimM542
Please do not submit duplicate posts.
Await the answer being posted to your original question.
You are correct, as your rental business commenced in August 2024, the first Tax Return you would complete would be the 2024/2025 tax year, which has an online deadline of 31st January 2026.
Guidance on deadlines for submission as well as for making payment can be found at:
Self Assessment tax returns: Deadlines - GOV.UK.
Thank you