This part of GOV.UK is being rebuilt – find out what beta means

HMRC internal manual

Capital Gains Manual

Debt on security: essential characteristics of: repayment at short notice

You cannot say that a debt is not a debt on a security simply because it can be repaid at short notice. But it is reasonable to suggest that in such cases there should be some compensation for the creditor to counterbalance the uncertainty as to the term of the loan. For example, a penalty can turn an otherwise uncertain, and therefore inherently unattractive, loan into a worthwhile investment. If a loan can be repaid at short notice, but there is no compensating benefit for the creditor, this would count against accepting the loan as a debts on a security.