With the tax deadline approaching, investors are deciding whether  to convert from a traditional IRA to a Roth IRA.

But before they do, advisors have one more conversion strategy to offer their clients, according to Fidelity Investments: the “charitable offset” strategy.

Fidelity suggests that clients donate to a charity with a donor-advised fund program, such as Fidelity’s Charitable Gift Fund, as an “offset” to help reduce the potential tax implications of a Roth IRA conversion in the conversion year. Yes, donors can give to any non-profit to help offset taxable income, but some may not want to make a large one-time donation to a charity. With a donor-advised fund program individuals can recommend several nonprofit organizations and can donate over a period of time.

According to a recent Fidelity survey of almost 500 tax advisors, 40% of investors working with tax advisors are eligible for a Roth IRA conversion now that income limits have been removed, and 35% are expected to complete a conversion by the end of this year.

Prior to Jan. 1, only individuals with modified adjusted gross incomes of $100,000 or less were eligible to convert assets from a traditional IRA or a 401(k) with a previous employer to a Roth IRA. Clients who want to convert funds from a traditional IRA to a Roth IRA have to pay taxes on the amount to be converted, but there is also a one-time provision in 2010 that allows clients to spread their tax income from the conversion equally over the next two years, 2011 and 2012.

Yet advisors say their clients express concern about converting to a Roth IRA with the biggest worry being the tax implications. This is where a charitable donation comes in.

“Making a charitable contribution to a donor advised fund is a strategy that advisors can use to help their clients offset the taxable income of a Roth IRA conversion, while at the same time establishing a “ready reserve” of charitable dollars that can be used to recommend grants on their own timetable,” said Sarah Libbey, president of Fidelity Charitable Gift Fund.

To reduce the impact of taxable income, Professor Chris Hoyt of the University of Missouri (Kansas City) Law School said in an article published on Fidelity’s website, that advisors may want to suggest to clients to make an offsetting charitable donation.

“The strategy is to try to get deductions you would have had in future years and accelerate them into the Roth conversion year,” he said. “The easiest way to do that is to be a philanthropist.”

Charitable contribution offsets may provide the added benefit of allowing clients to convert a larger percentage of the IRA balance without being bumped into a higher tax bracket.

Charitable donations can be in cash, publicly traded securities, C-corp shares and S-corp shares, depending on the donor-advised fund program, according to Fidelity. Donors may be eligible for an immediate tax deduction of up to 50% of adjusted gross income for cash contributions, or a deduction of up to 30% of AGI for contributions of securities. With long term appreciated securities, the capital gains tax can be avoided.

But David A. Handler, an estate attorney and partner at Kirkland & Ellis, said “it’s all a bit of a shell game.” If a client makes the Roth conversion they’ll have to pay income tax. What is one way to reduce income tax? Give the money to charity. “You’re not actually coming out ahead; you’re just reducing your income tax.”

Handler said a charitable offset strategy makes sense for those clients who were planning on giving money away to charity in the next few years anyway. For those clients, donating to charity will help offset some of the tax implications of the conversion, so the client will reduce their taxes and have the opportunity to donate to their favorite charity. “But if you have no intention to give to charity don’t try to give away $1 to save 40 cents. It won’t ever add up. You’re not ahead, but you didn’t give any to taxes.”