Hi there, I take it you are still in employment, and the form is No.12 ? All your income from whatever source will be combined and taxed. Your employer will hold the Notice of determination for Tax Credits and Standard rate cut off point, and NOT the ARF income provider. If this is the case the ARF Income provider will be obliged to deduct Tax & USC and if under 66 PRSI on an emergency basis. I have not filled in a Form 12 my self.
A) Where your combined income exceeds €32,800 for the tax year in question,2014,it will attract tax @41% on any balance that exceeds this amount.
B) Your income statement,Payslip from The ARF provider will show Tax USC, PRSI deductions for the year. This will show on your P60 from employer,after end of tax year,the following February, of Tax USC deducted with PRSI. What needs to be done is request a balancing statement,P21, as it will be most likely that all the income will have the correct SRCOP and tax credits applied.
C) If your combined income from whatever source does not exceed €32,800 your tax will be 20%.The revenue does not discriminate whether it is ARF or Employers's Salary, if it exceeds what is stated in A) above it will be taxed @ 41% If you are requested to enter info on form 12 it may indicate "Employer"
The usual providers of ARF income e.g. Standard Life, Irish life etc. are regarded as "Employers" so check with Revenue if this is the case. I hope this helps somewhat.