It is income, the operator of the site is legally required to notify HMRC that you are receiving income. You are on a list.
£10 a month is on the low side. If you are paying income tax on earnings it is possible to have an informal code adjustment - but then HMRC will be checking.
For £10 a month I would suggest you phone HMRC (number on gov.uk), you may be required to register for Self Assessment - and if you intend growing the income you may as well register now and getused to the system.
Answers & Comments
It is income, the operator of the site is legally required to notify HMRC that you are receiving income. You are on a list.
£10 a month is on the low side. If you are paying income tax on earnings it is possible to have an informal code adjustment - but then HMRC will be checking.
For £10 a month I would suggest you phone HMRC (number on gov.uk), you may be required to register for Self Assessment - and if you intend growing the income you may as well register now and getused to the system.