Almost 8,000 special needs assistants are set to ballot for industrial action.
IMPACT said it has issued ballot papers as a result of the government's failure - for the fourth year running - to announce how many will be allocated to schools before the end of this year's summer term.
The ballot for industrial action, up to and including strike action, is to ensure there is a guarantee that they are given the information no later than May.
It is also calling for procedures to be put in place for dealing with special needs assistants (SNA) grievances.
The ballot will conclude on October 13.
IMPACT assistant general secretary Barry Cunningham said the lengthy delays to their publication every year since 2014 means SNAs are uncertain if they have a job to return to.
“The delay may also leave them unable to apply for redeployment in the event that they don’t have a job. There’s no practical reason why the schools cannot get the figures in April or May, so that they can plan for the new school year in a dignified, effective and timely way.
“The habitual failure to do this simple thing, which means so much uncertainty for our children and their schools, also means that SNAs don’t know if they have a job to return to each year. That it happens every year shows contempt for SNAs, and for the children, parents and schools they serve,“ he said.
Mr Cunningham said IMPACT will no longer accept the delays in the publication of SNA allocations.
"Our objective in balloting our SNA members on this matter is to gain an absolute commitment from the Department of Education and Skills (DES) and the National Council for Special Education (NCSE) that the annoubcement of SNA allocations is made in sufficient time to allow a smooth transition to the next school term."