by mullet on Mon Jun 28, 2010 10:18 pm
NI is based on pay periods, be they weekly, fortnightly or monthly. If your employer runs the payroll weekly but you submit fortnightly claims, then is it possible that you are at fault here? But if fortnightly claims are expected and submitted, then the pay period should be 2 weeks.
For 2009-10 you would need to contact the NI office at Longbenton to discuss a refund. For the current year you need to argue it out with your employer.