NEW YORK (MainStreet) — If there's anything worse than having to do your taxes, it's finishing the paperwork and finding you don't have enough money to pay what you owe.

That's a bigger concern in 2015, as 3 million to 6 million Americans will owe the federal government money for not having health insurance, or who got Obamacare subsidies but saw their income rise during 2014, according to a CNN report.

(If you believe you fall into that category, the Tax Policy Center has a handy-dandy calculator to figure out your penalty from your health care insurance experience.)

Americans who have owed Uncle Sam some tax money don't look back at the experience fondly, but note the IRS has grown flexible in recent years.

"I've owed the government a few thousand dollars in the past," says Joe Lopez, an Orlando, Fla., real estate agent. "The one thing you don't want to do is ignore them. They are more than willing to set up a payment plan if you call them."

Lopez says to expect an hour wait on the phone to talk to an IRS agent, and advises bringing in a tax professional. "Get a second opinion from a tax preparer," he says. "I did, and the tax preparer was able to re-file two years of returns. When we added in missed deductions, the IRS actually owed me money."

Michael Raanan, a former IRS tax collection agent and current president of Landmark Tax Group in Orange County, Calif., tax services firm, says whatever you do to make sure to file your taxes even if you do owe money. "Negotiating with the agency cannot commence until they are deemed in 'current compliance' with their federal tax obligations," he says. "This means you first file all required returns … and be current with estimated tax payments or withholding."

"Meeting this requirement will establish good will with the IRS and help to facilitate a favorable outcome of your tax dispute," Raanan says.

Eric Rothenberg, a tax attorney and partner at Needham, Mass.-based Oar Lawyers, advises knowing the rules and frameworks the IRS uses to deal with late payments. "If you owe only the current year and meet this test, you can file Form 9465 with your return filed timely, but you cannot pay in full," he says. "There you're eligible for a guaranteed installment agreement if the tax you owe isn't more than $10,000." That's also the case if, during the past five tax years, you (and your spouse, if filing a joint return) have filed all income tax returns on time and paid any income tax due, and have not entered into an installment agreement for payment of income tax, Rothenberg notes.

You can also earn an installment agreement if you agree to pay the full amount you owe within three years and to comply with the tax laws while the agreement is in effect. "It's also the practice of the IRS to grant these installment agreements even if you can pay your liability in full — if the tax you owe is not more than $10,000 and you meet the other criteria," he adds.

If you're considering using a firm that touts itself as a tax relief specialist for consumers owing back taxes, tread cautiously.

"We see so many clients using national tax-help companies who advertise on late-night television and wind up paying a lot of money for offers that have no chance of success," says Eric Green, a partner at Green & Sklarz, a New Haven, Conn., legal services firm. "Taxpayers should be able to sit down with their professional and have that professional explain to them what the offer or payment plan will be, and why."

"There is no such thing as a 'proprietary strategy' in this area," he adds. "If the taxpayer hears that, run in the other direction."

— Written by Brian O'Connell for MainStreet