Broadly you (OP) have understood it correctly. If your self employed earnings are below a certain limit (2012-13 = £5595) - goes up each year by about £200 to £300 or so for inflation - then you can apply for exception from payment of class 2 NIC (on form CF10). If you have other earnings from (eg) employment on which you pay class 1 contributions, then it is a no-brainer: go for it, as the class 1 contributions will buy you all the benefits. However if the self-employment is the only income source, then for each year that you claim exception, that year also does NOT count toward your entitlement to contributory benefits. If state pension is the only thing that concerns you, then you need (at present) to have 30 years "paid up" during your working life, which normally lasts more than 30 years so a few years of exception probably would not make much difference. You need to bear in mind that the class 2 contribution is fairly cheap in the scheme of things, but if your only income source is bringing in less than £6K I guess that every little helps.