Hi
Thank you for your question, I refer you to PIM4010
Rent-a-room: exemption limits which states- Individual moves leaving lodger
The are circumstances in which the qualifying individual with a lodger, moves to a new home leaving the old home unsold and the lodger in occupation. Rent from the letting may, in these circumstances, continue to qualify for rent-a-room relief until the end of the basis period during which the qualifying individual moved.
If, after the individual moves, the lodger is allowed the use of the whole house (whether or not extra payment is involved) you can accept that:
• the existing source continues,
• the basis period does not therefore end at the date of the extension of the occupation,
• the rent-a-room conditions are satisfied until the end of the basis period (but no longer).
Following the end of the basis period the following guidance will apply, which is still PIM4010 and can be located on the same web page as the above guidance - Taxpayer moves abroad
If a taxpayer lets their home in the UK while they live abroad, they will not normally be within rent-a-room. This is because the let property will not usually be a residence of theirs at any time during the basis period for the letting. See below for more detail.
Regarding the expenses part of your question, I refer you to HS223
HS223 Rent a Room Scheme (2024) which gives the following guidance of the 2 methods used to calculate your tax- 1.2 If your gross receipts are more than the Rent-a-Room limit
If your gross receipts are more than £7,500 (or £3,750), you can choose how you want to work out your tax:
Method A
You pay tax on your actual profit — your total receipts less any expenses and capital allowances.
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. You will continue to pay tax on your gross receipts over the Rent-a-Room limit until you tell HMRC that you want to change back to paying tax on your actual profit (Method A).
If you pay tax using Method B, this automatically stops if your rental income drops below £7,500 (or £3,750) limit.