Property tax

So I haven’t lived in Dublin for a long time and just heard today off my mum (pensioner) that she hasn’t being paying the LPT on her house since it came out. She owes something like €33000!!! She said she deferred it until she dies and it would be paid on the sale of the house but I don’t think she was eligible for deference according to what I’ve read on the website, which is fairly confusing to wrap my head around with all the different bands and added interest she has probably accrued!

Anyone got experience with this that could guide me? Any advice appreciated! Thanks