I'm in a similar position to the OP. In short you have 2 choices:
1. Something called top-slicing, whereby you can reclaim the additional tax you over-paid. For example I've been paid for Jan, and then a lump sum for Feb and Mar. However I was paid it all as January salary, at 40%, so I paid far more tax than if that amount was spread over the 3 months. I'm due back all the extra tax I paid had my employer kept me on the pay-roll to end-March.
2. Leaving statutary redundancy aside, as none of us were due any (not in job for more than 2 years), you are allowed up to €10k as a tax-free lump sum when made redundant, claimable only once every 10 years.
For both options, the Revenue will need to know what the
Taxable Lump Sum was. The TLS for me is everything EXCEPT my normal Jan salary, which was Jan 1st - Jan 21st, the day I was laid off.
To calculate the TLS (assuming its not listed on you P45) I need a letter from my employer with a detailled breakdown of amount paid in Jan.
Say I was paid 15k in January's salary:
4k was salary for Jan1-21st
2k was payment for holidays carried over from last year
5k was an ex-gratia redundancy 'bonus'
4k was payment for my notice period (28 days of Febuary).
Leaving aside Jan's salary, I have 11k remaining. This 11k is my TLS. I should be able to claim 10k of that as a tax free lump sum, and reclaim the tax from the Revenue.
thats the plan anyway