Your IELTS certificate (or other proof of English ability) needs to be no more than two years old at the time you submit your ITA.
https://www.immigration.govt.nz/opsmanual/#66777.htm When an ITA arrives, clerks look over the form and the evidence to check whether everything apparently meets the requirements, and if it doesn't, they can't accept and lodge it, so it'll be sent back.
Similarly, if the employer's name is on the non-compliant list when your ITA arrives, it will be sent back, not lodged, for that reason.
Any application to INZ is a legal document, and by submitting it, you are warranting that everything that is in it is the truth, right then. INZ aren't allowed to accept anything that only
probably will be true at a later date (because things can go wrong, even with matters that people believe in all honesty are going to happen).