You can just ssay that you object.
Not entirely clear why you are going to the EAT but I assumme you are going to obtain a determination that you are entitled to a redudancy payment when you never got one - then it is the EAT not the Rights Commissioner that you will have to get that determination from (thats what is providsed for in the REdudancy payments act 1967). I think you then take that to the Redudancy payments scheme to be paid the statutory amount on foot of the EAT determination.
it is a simple enough process and you can do the EAT yourself. Bring any documents (contract, pay slips , P60 ets) that demonstrate that you worked there when you say you did.
THey will be very helpful. After the hearing on the day they may (or if not Secretary of the EAT on the day) will probably give you a steer on what to do next, ie where to send it. If you can't find out as citizens advice.
hope that helps.