Ottawa’s plan to temporarily boost the federal GST credit and issue a one-time payment to Canadians is expected to cost $12.4 billion over five years, according to new estimates from the Office of the Parliamentary Budget Officer.

The budget watchdog says the proposed one-time payment, expected this spring, would cost the federal government just over $3 billion in the current fiscal year. Ongoing increases to the GST credit are projected to add between $1.7 billion and $1.9 billion per year through 2031.

Prime Minister Mark Carney announced the measures last week as part of the federal government’s response to ongoing affordability pressures, particularly rising grocery costs. The plan includes a 25 per cent increase to the GST credit over the next five years, along with a one-time payment worth 50 per cent of the annual credit.

The GST credit is currently paid quarterly and is targeted at individuals and families with low and modest incomes. The Parliamentary Budget Officer estimates more than 12 million Canadians would qualify for the enhanced support, including many households in British Columbia and Alberta that have been affected by higher food and housing costs.

Conservative Leader Pierre Poilievre has said his party will support the measure in Parliament, though he has criticized it as a short-term fix that does not address broader cost-of-living concerns.