PSD specifies that SEPA transfers are D+1, meaning the transfer should arrive no later than the next working day.
BOI state here that for personal customers using online services, there is a 2:30pm deadline. There are different rules for business customers, and for counter transactions etc.
In my experience, the majority of transactions arrive next day and same day isn't unheard of. But it can occasionally take longer, especially if you go anywhere near a weekend.
There is also a "same day value" service available form most of the banks if you need it, costing something like €25. It us usually used for high value transactions, contract closure etc and has its own set of cut off times (usually needs to be initiated before midday). .
Wrong. The payment cut-off on AIB's iBB is 14:00 for payments "From your AIB ROI Accounts to Third Party Accounts in other financial institutions" and AIB state "Value may be given on the same business day for any amount if the payment is made before 14.00 on a business day. Payment execution is a maximum of one business day." Hence my statement "the majority of transactions arrive next day and same day isn't unheard of".