Ramsey MHK Lawrie Hooper will ask for Tynwald's backing to change tax laws for couples next month.
When the court sits in April, he'll ask members to give joint income tax treatment to cohabiting couples - after being told earlier this year there were no plans to do so.
He wants the Treasury to include the changes in its next tax legislation.
Tynwald is due to sit from Tuesday, April 21.
Yacht club worries over lifeboat retirement
One nuisance cyclist ticketed in more than three years
New ministerial post created by chief minister
Huge floating book fair to arrive in Douglas next month
Stay safe for Hop Tu Naa tonight
Special Olympics fundraiser needs you
Peel ready for bonfire and fireworks later
Government: "UK never told us about child murderer"