Tax return problem..?

i just filled out my tax return, and it shows i've got �0.60 tax underpaid from employment, which i found ridiculous. i already hate myself for getting myself into this self essment mess just because i made �50 pounds from self employment 2 years ago. anyway,my last year's return shows �240 overpaid, why can't they just deduct the underpaid tax from the �240 which i haven't yet claimed? are they actually going to make me pay the �0.60? i've done the return online, will i be getting like a bill now or something? thanks..