You should get it by the 25th of March every year.
That gives you ample time to complete your Tax Return and hand it in to the receiver of revenue. You then don't have to wait for the last minute...
Your employer is legally obliged to prepare all PAYE 5 forms by the 25th of March and then hand in a reconciliation to the receiver of revenue. If they have not prepared your PAYE 5 by the 25th of March they are contravening the law.
Thus, if you have not received your PAYE 5 by the 25th of March, speak to your employer. Don't wait until the last minute.
The onus is still on you to submit your taxes in time.