Does DS giving me £40 per week for food and washing come under Rent a Room?

[crepeyneck]

Anywhere I can officially check?

He is just about to move back home and not sure what to do.

Look at the hmrc website and guidance

if he is part of your family and contributing to the household , what has it to do with the tax man?

You can take £4K for rent for your house per annum without having to pay tax.

How old is your DS?

What is rent a room?

next year the rent a room allowance doubles
BUT
there are restrictions on family members claiming their rent as expenditure

No it doesn't, you can accept £4250 without having to pay tax - check the gov.uk website

You're far below the threashold

www.gov.uk/government/publications/rent-a-room-for-traders-hs223-self-assessment-helpsheet/hs223-rent-a-room-for-traders-2015

No, it doesn't. He's family. He's making a normal contribution to the running of the household. You wouldn't include a spouse under the rent a room scheme, so you wouldn't include a child either.

Payments made by family Memebers towards household expenses are not taken into account so you don't need to worry . Rent a room is so you can rent out your spare room to non family members