Bus Éireann is to issue temporary tickets to thousands of school students following problems with a new computer system.
Parents have reported delays receiving annual bus tickets, which are used by around 115,000 primary and secondary students.
Families have paid up to €650 for an annual school transport ticket, but as pupils return to classrooms, thousands are still waiting for their ticket to arrive.
The delay has been blamed on the introduction of a new, centralised computer system.
In the past, school bus tickets were issued at local offices.
The latest figures show only 82,000 tickets have been issued and some of these are still in the post.
Temporary tickets are now being issued via email, and families are being advised that evidence of payment will also be accepted on buses this week.
Bus Éireann has a helpline number which will be open from 9am to 8pm all this week - 1800 945 945.
Speaking on RTÉ's Morning Ireland, Bus Éireann spokesperson Nicola Cooke said there had been minor glitches with the IT system which had caused a delay, and the payment deadline then had to be extended.
Ms Cooke said the company was now slightly on the back foot.
She apologised for the inconvenience and asked people to bear with the company as it attempted to address the problem.