The voting started on Monday and will run until Friday, which is when the votes will be counted.

The union doesn't support the proposal and says almost none of the issues have been resolved, but the mining company said it was "proud of the offer" it had made.

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Since the end of August, there have been rolling strikes, including a two-day stop-work meeting where hundreds of miners gathered in Gunnedah.

CFMEU northern NSW vice president Jeff Drayton said there were "still a number outstanding issues".

"We've continued to meet with the company, but we haven't been able to resolve the issues," Mr Drayton said.

The union says it wants the same pay packet, bonus structure, access to independent arbitration and sick day arrangements Idemitsu has with its Muswellbrook and Ensham mine workers.

The wage increase on offer was $45,000 less a year than what Idemitsu paid to employees at their open cut mine in Muswellbrook, CFMEU officials claim.

Boggabri Coal chief operations officer Steve Kovac said he was hopeful the majority of workers at the mine would support the offer Idemitsu had made to ensure stability and security for their families in the lead up to Christmas.

Idemitsu said the enterprise agreement provided "generous remuneration, terms and conditions and ensure mine operations remain sustainable into the future".

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