The toughest thing about sending a child to college is signing the tuition check. The second-toughest thing is figuring out how to get the biggest chunk of that money back from Uncle Sam.

This year there are three tempting but puzzling tax breaks. In addition to the Hope and Lifetime Learning credits, there’s a deduction worth up to $3,000. The trouble is you can’t claim more than one per student — and identifying which one will save you the most money will depend upon a raft of variables such as your income, your expenses and whether your student is a junior yet.

“Too bad Congress didn’t have a little more education before they passed this law,” said certified public accountant Sharon Kreider of Sunnyvale, Calif. “There’s no reason it should be this complicated.”

The rules are complex for two reasons. First, Congress wanted to aim these tax breaks primarily at middle-class families who generally don’t qualify for college aid. Second, the rules are devised to ensure that families don’t double-dip by getting two tax breaks for one education bill.

Here’s how the tax breaks compare:

• The Hope credit is worth up to $1,500 per student. That’s a dollar-for-dollar credit on the first $1,000 of qualifying expenses, plus 50 cents per dollar on the next $1,000. It can be used only in a student’s first two years of post-secondary education. (Even that’s a tax-planning riddle, because the freshman and sophomore years typically span three calendar years.)
• The Lifetime Learning credit is worth up to $1,000, refunding 20 percent of the first $5,000 you spend. Unlike the Hope credit, you can claim it an unlimited number of years, even if you are just taking courses to improve your job skills.
• The tuition and fees deduction allows you to take an “above-the-line” deduction — meaning it reduces your adjusted gross income — for up to $3,000 of post-secondary expenses. By writing it off on the front page of your 1040, it doesn’t get a haircut like miscellaneous deductions you must itemize on Schedule A.

All three tax breaks have one thing in common: You’ll lose them if you’re income is too high. For couples who file jointly, the credits begin to phase out when their adjusted gross income hits $82,000, and they lose them entirely when adjusted gross income crests $102,000. Divide those amounts in half if you’re single.

The phase-out for the new deduction is significantly higher — up to $130,000 for couples and $65,000 for singles.

The only way to discern which tax break is best in your case is to crunch the numbers, experts say. Still, here are a few rules of thumb:

• If you qualify for all three, the Hope is probably best.
• If you must choose between the Lifetime credit and the new deduction, the key variables will be your actual expenses and your marginal tax bracket. To max out the $1,000 credit, you need $5,000 of expenses, while the deduction is based on $3,000 of bills. And, generally, the value of the deduction will rise along with your tax bracket. It can save you $810 in the 27 percent bracket and $1,158 in the top 38.6 percent bracket.
• You might want to forgo a credit, however, if the deduction would lower your adjusted gross income enough so that you’d qualify for unrelated tax breaks such as the retirement saver’s credit or the earned-income credit.

“You really have to work out” the what-if scenarios, said Bob D. Scharin, editor of Warren, Gorham & Lamont/RIA’s Practical Tax Strategies journal. “We really don’t have tax simplification here.”