Income Contingent Repayment (ICR) loans are the type of student loans which were made available from 1998 onwards to higher education students. These loans are repaid based on income, normally via deductions from a customer’s salary if employed or through Self Assessment tax return if self-employed.

https://www.gov.uk/government/publications/numbers-of-repayment-customers-liable-to-repay-that-have-not-made-any-repayments