What happens if I'm late paying my taxes on my payment plan for 2009's taxes (the ones to be filed in 2010)?

Where I work they don't take out for state taxes so my tax person set me up on a payment plan where I pay so much every 3 months. That way, come 2010 when I have to pay for 2009 taxes it won't be that high. I missed a payment for one of my scheduled dates and I was wondering if I would get penalized for it, even if it is for next year? (I can't afford to send it in until next month)