Terminally ill internet star Alice Pyne has been told that her mother's child benefit could be taken away unless she goes to college.
Home-schooled Alice, 16, came to international prominence when a list of the things she wants to do before she dies was posted on the internet last year.
The teenager has been fighting Hodgkin's lymphoma for five years.
Alice and her sister Milly, 13, from Ulverston in south Cumbria, also received the British Empire Medal this year for services to charity after raising more than £100,000.
A spokesman for Her Majesty's Revenue and Customs (HMRC) said every parent whose child would be turning 16 automatically gets a letter saying that their child benefits would be stopped unless the child continued full-time "non-advanced" education or started an "approved" training course.
The spokesman said although he could not give specific details about Alice's child benefit payments, her case was now being investigated by the HMRC and her parents are being contacted.
"We are contacting her parents just to find out what the circumstances are in this case," he said.
Alice wrote on her Facebook page on Wednesday: "my mum has just had a call saying that my child benefit has been stopped because I'm no longer in full time education.
"Mum removed me from school 4 years ago because basically, they weren't interested in me once I became ill, they didn't visit and the only stuff we got from them was the bill every term.
"We said that my home education is continuing, but apparently, I should be getting a job if I'm not going to go to college! So payments have been stopped and we've to wait for an education specialist to consider it."
The HMRC spokeswoman said that parents in the UK can apply to receive £20.30 a week for their eldest child and £13.40 a week for each of their other children under 16.
Barrow and Furness Labour MP John Woodcock said the Pyne family did not deserve to be treated in this way.
"Sending an unfeeling and unhelpful letter through the post to deprive a terminally-ill child's mum of child benefit is a callous way to deal with a family who are clearly an exceptional case," Mr Woodcock said.
- On her "bucket list", Alice wrote that she hoped that everyone in the UK would sign up as a bone marrow donor. Other things on the list included going to her school leavers' prom, swimming with sharks and meeting Take That, which have all been done.