The Department of Education has spent almost 11 million euro posting payslips to current and retired school staff over the past five years.
According to freedom of information figures, the biggest bill was last year.
Primary and post-primary teachers are paid every two weeks and receive a paper payslip from An Post for each payment.
Over 3.4 million payslips to current and retired school staff were posted in the 2021/2022 school year, costing nearly €2.6m.
It's an increase on the previous year, when the postage cost less than €2.2m.
The total bill since the 2017/2018 academic year is over €10.9m.
The department says there are around 135,000 staff paid every two weeks.
This includes current and former teachers and non-teaching staff of primary, secondary, community and comprehensive schools.
The department says it intends to offer current and retired staff electronic payslips in the coming months.