Both groups pay 9 per cent extra marginal tax to repay their loans, but Plan 2 borrowers’ higher debt means this takes far longer. And the loan rate means two-thirds of repayers are piling up interest faster than they can pay it off; in the last tax year, £15.2bn of interest was added to loans, but only £5bn repaid. Borrowers must earn £66,000 a year before they start paying off any of the principal, estimates the Institute for Fiscal Studies.