In his mid-30s, Mr. Buck started making small annual RRSP contributions. But only when he left a job as an agricultural researcher at the University of Guelph in 1993 did the plan really begin to grow. "At that point, I rolled my pension plan into my RRSP and Barbara used an inheritance to open a plan."

Soon after, however, both Bucks cashed in some RRSPs to start businesses -- Mr. Buck launching AgriTours, an agriculture tour company, and his wife becoming a sales rep for Crabtree & Evelyn personal-care products. While they kept contributing to their RRSPs, the size of those contributions was limited by other financial obligations.

Today, the Bucks each have about $130,000 in RRSPs. That may sound impressive, but it's a long way from the $500,000 apiece that Mr. Buck, now 49, and his wife, 47, figure they will need to retire at around age 65.

"I don't want to depend on Old Age Security and a small amount of personal savings like my grandparents who lived into their 90s," he explains.

Unfortunately, this year, the couple is not in a position to maximize their contributions. Last year, Mr. Buck says, "was difficult business-wise and we're focused on rebuilding this year."

The Bucks are not alone. Like many Canadians, they are sitting on a substantial amount of unused RRSP contribution room -- Mrs. Buck has $20,000 and her husband, $18,000.

Since 1991, Canadians have been allowed to "carry forward" unused contribution room indefinitely; that unused room has now reached a cumulative total of $306.5-billion, according to Statistics Canada.

Those who want to play catch-up have several options, says Don Douglas, vice-president of RBC Dominion Securities in Toronto.

One of them is to take out a loan. It's a strategy that Mr. Buck uses, borrowing $2,500 to $3,000 annually, then using some of the resulting tax savings to repay the loan. He also makes sure to retire the loan before the next year's RRSP season arrives.

That approach gets a nod of approval from Michele Wood-Tweel, a Halifax-based partner in KPMG's personal financial-planning practice.

"With interest rates so low, the current borrowing environment is very favourable," she notes. "But it's important to repay the loan within a year. Otherwise, it starts to feel like an albatross, particularly when markets are falling."

For those who can't repay the funds within 12 months, Ms. Wood-Tweel recommends a program of automatic monthly withdrawals from your bank account. "Make it a reasonable amount and you'll learn quickly to live without the money," she says.

Another option is to make a "contribution in kind."

"Many people don't realize that they can make contributions in kind," Mr. Douglas says. If you have eligible assets, such as Canada Savings Bonds or other non-registered investments, including mutual funds, you can transfer them to your RRSP without cashing them in.

Be aware, however, that "when you contribute stock, you have to claim any existing capital gain. But CSBs don't trigger capital gains and they generate a high amount of tax-sheltered interest income," Mr. Douglas says.

Lump-sum contributions, if you can come up with the cash, are the quickest way to beef up RRSPs. Bonuses and inheritances are great sources of ready cash, Ms. Wood-Tweel says, "provided you can live without the money as part of your cash flow."

"You can transfer a bonus without tax withholding if your employer has a group waiver," she notes. "Otherwise ask Canada Customs and Revenue in advance to reduce your tax deductions at source."

You will need to establish that you have sufficient RRSP room, that your tax returns are up to date and that you don't owe any money in back taxes, she says.

Another lump-sum source is the sale of a property, such as a cottage, she says. "Look at your personal-use assets. If there's something you can live without, why not part with it, take the cash and move on?"

While the sale of such a property could create a capital gain, you can reduce your tax liability by contributing some or all of the proceeds to your RRSP, she says.

If you're able to make a large catch-up contribution, you don't have to take the deduction right way. In fact, you may be well-advised to delay it or spread it over a period of time.

"Suppose you received a $40,000 inheritance. You can contribute the money all at once and, depending on your taxable income for the year, delay the deductions until you're in a higher bracket. There is no time limit over which you can deduct the contribution," Ms. Wood-Tweel says.

Joe Hamley, a partner in Guelph, Ont.-based Acorn Financial Services, warns against contributing to your RRSP, "in a non-tax advantaged way.

"Suppose your taxable income for 2001 is $40,000 and you have $20,000 in unused contribution room that you want to use up. You would pay 28-per-cent tax on the first $10,000 of your taxable income and 22.1 per cent on the rest. So you're better off to deduct $10,000 of the 2001 RRSP contribution this year and save the rest for a subsequent year."

Once the money is in your RRSP, some latecomers may be tempted to shift to higher-risk investments to maximize their returns. But Mr. Douglas urges caution.

"Everyone wants their portfolio to grow but they sometimes forget about capital preservation and learn too late that they're risk-averse," he says.

"Determine your investment style and your objectives in advance and make choices you're comfortable with. The more you understand your investments, the better you'll be able to handle the ups and downs in the equity markets," he adds.

Mr. Hamley has some consoling words for those who made a late start on their RRSPs.

"I work with many people like that and I tell them that it's not really necessary to start early. If you start at 45 and retire at 65, your retirement will cost less than for someone who started in their 20s and retires at age 55."

The important thing, he says, is to use up your accumulated contribution room as soon as you can afford it.