It is understood the move will mean some workers will see their pay fall by hundreds of pounds a month.
Earlier this year the company announced a round of redundancies in response to reduced global demand for its products.
Terex is one of Northern Ireland’s largest manufacturing employers with about 2,000 people employed in factories in Omagh, Dungannon, Ballymoney, Londonderry and Cookstown.
It also has a business services centre in Lurgan.
The company makes crushing and screening equipment used in industries like construction, mining and recycling.
In July it said an “extraordinary surge in demand” for its products in the aftermath of the coronavirus pandemic had now "stabilised" and it needed to cut costs as a result.
It added that it would also reduce overtime and travel, as well as not filling some vacant posts.
The broad construction equipment sector in the UK and EU has also come under pressure from Chinese exports, partially prompted by reduced demand in the Chinese domestic market.
