How to tell HMRC to use method B for the Rent a room scheme

Hello, starting from today I'm taking in a lodger. The expected income is £900 per month. If I understand the instructions correctly: - for the 2023-2024 tax year I won't have to declare anything because the amount will be less than 7500 - for the 2024-2025 I will have to declare the different between 10800 and 7500, if things go to plan. Is it correct? I want to use method B. Quoting the the instructions: " Method B You pay tax on your gross receipts over the Rent-a-Room limit — that is, your gross receipts minus £7,500 (or £3,750). You cannot deduct any expenses or capital allowances if you choose this method. HMRC will automatically use your actual profit (Method A) to work out your tax. If you want to pay tax using Method B, you need to tell HMRC within the time limit. " How do I tell HMRC that I want to use method B? Do I have to write a letter to HMRC? If so, to which address? Or do I have to select a box in the self-assessment? Also, what's the time limit? Thanks and regards.

Hi,
You are correct, when applying Rent-A-Room relief, you would only have to declare the difference between your gross rental income and the exemption amount of £7,500.
In terms of time limit, you must let HMRC within one year of 31 January following the end of the tax year if you want to start or stop paying tax on your gross receipts over the Rent-A-Room limit (Method B).
Thankyou.

Hello, thanks for your answer. How do I have to tell HMRC that I elect to use method B? Do I have to call them at the telephone or do I have to send a letter? In the latter case to which address and to which team? Thanks and best regards.

Hi,

As the income will need to be declared in a Self Assessment tax return, your method of calculating your profits will be shown by the way the rental income section is completed.

Thank you.