late service charge for the tax year reported by management company using section 20B(2)

Dear Sir, I will fill in the Self Assessment for 2023-2024 with a deadline by the end of October. However, the management company then sent a letter informing me that additional cost was incurred for the year ending 31 December 2023. I have not yet received the invoice and if it comes later than the deadline for self-assessment, how can I report the loss? Since the earnings from the rental are little, I would lose the money from paying more tax than I should. ( Next year, there will be high service charge demand for cladding remediation as well and surely the rental income would become negative then)

Hi,
You can still submit your 2023-24 tax return by the due date.
Once you receive the details from the management company you will have until 31 January 2026 to submit an amendment to your return.  
For more information please see Self Assessment tax returns If you need to change your return
Thank you.