I think if you're not earning over a specific amount, then you don't have to pay... at least that's the rule if you're in the UK and, for example, earning less than the threshold so assume it would be the same if you were abroad. Not sure what proof they'd requite about lack of earnings though and you will be accruing interest (though at a lesser rate than most debts) whilst the amount owed stays the same so depends on your plan in the long term. I think it's 30 years before they cancel it isn't it?