When you receive IB,and submit to your employer,then your payroll department enters that on their system.This captures IB for the purpose of correctly taxing it.If your employer did not do this then,the Revenue receive that information from Dept of Social Protection,unbeknown to your payroll dept.So when P21 Times comes around it shows an underpayment.Check your payslip,and see if IB was entered on payment details,if not the it was not ran through Payroll.I suggest you approach Payroll and point this out.If the problem is for current year,2014,then it can be run through for this year.For other years,only to 2009,then get your employer to declare that the IB payment was remitted to them,without payroll adjustment,and re-submit it with employer's Declaration to revenue.One other item IB and other DSP payments are not subject to USC/PRSI so you would be due a Refund on the IB you received.PRSI from DSP.Class A,E,H,&P of PRSI are entitled to Ilness benefit,I hope this helps,as I was in the same situation,and I obtained the required result.