The Conservative government is doubling the children's fitness tax credit in time for parents to file their taxes next spring, Prime Minister Stephen Harper said Thursday.

The government will also make the credit refundable starting in 2015, which lets low-income families take advantage of the credit, too. A credit that's non-refundable means parents whose incomes are too low to pay taxes don't save any money.

The maximum expense that can be claimed will go from $500 to $1,000. Parents can get back up to 15 per cent of their children's registration or membership fees come tax time, making the new maximum refund $150. Accommodation, travel and food are not eligible for the credit.

The tax credit was introduced in 2006 to encourage physical fitness among children. The government says it applies to 850,000 families.

The tax credit applies to children under 16, or under 18 if they're eligible for the disability amount.

Eligible activities, according to the Canada Revenue Agency, "include strenuous games like hockey or soccer, activities such as golf lessons, horseback riding, sailing, and bowling, as well as others that require a similar level of physical activity."

That includes supervised children's activities that run for at least eight consecutive weeks or, in the case of children's camps, five consecutive days and that require significant physical activity.

Fees for school extracurricular programs are also eligible too, says the agency.