Toronto lawyers filed the appeal on behalf of four Alberta fathers ordered to make immediate child support payments stretching back as far as 1997.

The appeal was launched to challenge an Alberta court decision in January that required fathers to pay large sums of money in child support based on changes in their incomes over the years.

In one case, a man was required to pay more than half of his annual earnings.

The fathers were paying child support according to prior court orders and separation agreements, lead counsel Deidre Smith said from her Toronto office.

One of them “is about as opposite from a deadbeat dad as you can get,” Smith said.

“(He is) being whacked with this significant retroactive award when a trial judge has said, `Hey, buddy, you did everything you are supposed to do.”’

The fathers can’t be named because of a publication ban.

“They really resent being called deadbeats or being told by the community that they haven’t taken care of their kids when they’ve been paying what the court order or agreement told them what to pay,” Smith said.

The problem has surfaced because federal payment guidelines announced eight years ago have not been fully implemented, she added.

When the guidelines were introduced, Ottawa included a process by which the government could calculate child support payments based on tax returns and notify parents of required adjustments in pay.

But the provinces had to sign on, which hasn’t happened.

As it stands, separated or divorced parents receive a court order telling them how much they owe, or work out an agreement with their lawyers.

But as child access arrangements change, parents remarry, have more children and incomes fluctuate, the original support arrangement often no longer accurately reflects each parent’s situation, Smith said.

“We know that statistically the vast majority of Canadian dads have increased income after separation,” she said. “If they went back and looked at their old orders, there probably would be additional support owing. I’ve got to think it’s in the millions.”

Virtually anyone who is paying child support under a court order or separation agreement made within the last 15 years may face large amounts of back claims, she noted.

One of the divorced fathers involved in the appeal has been ordered to pay $100,000 in retroactive child support, more than half his current annual income. Another father, whose annual income has never exceeded $23,000, has been instructed to pay an additional $10,000.

The court is expected to begin hearing the appeal between February and May next year.