If you took advantage of the $7,500 first-time home-buyer credit two years ago, you had better remember to include your first repayment of that loan on your 2010 tax return, which is due April 18.

Under the Housing and Economic Recovery Act, certain homeowners were eligible for a tax credit equal to 10 percent of the purchase price of a home, up to a maximum of $7,500. Married individuals filing separately could get a $3,750 credit. Unmarried people who jointly purchased a home were allowed to divide the credit.

Buyers jumped at the opportunity. Now the repayment process is causing the Internal Revenue Service some frustration.

It was never fair to call the original first-time buyer stimulus a credit. It was an interest-free loan. Those who took the credit are required to repay the government over 15 years in equal installments for any amount received. So if you qualified for the maximum credit of $7,500, this means a yearly loan payment of $500. The loan/credit applied only to homes purchased after April 8, 2008, and before Jan. 1, 2009.

To further boost housing sales, Congress added two additional tax breaks for home buyers. Which credit you claimed depended on when you purchased your home. An $8,000 credit became available for qualifying first-time buyers who generally closed between Jan. 1, 2009, and April 30, 2010. If you had a binding sales contract signed by April 30, however, you had up to Sept. 30 to complete the sale and still qualify for the credit.

A third credit of $6,500 was created for long-term homeowners who purchased a new or existing home between Nov. 7, 2009, and April 30, 2010.

People who took advantage of the $8,000 or $6,500 tax credit but then sold their home, or if the property was no longer their principal residence within three years of the purchase date, are required to pay back all of the credit amount.

I wasn’t a fan of any of the buyer credits, but I particularly didn’t like the $7,500 one because of its loan feature. If the buyer sells the house before the $7,500 credit is paid off, the entire amount becomes immediately due.

There’s another feature of the $8,000 and $6,500 credits. If the property is sold before the residency stipulation is met, and the gain is less than the credit, buyers only have to repay up to the amount of the gain.

Got all that?

I ask, because with all those caveats and three credits, it didn’t surprise me when the IRS said it was having problems processing some returns. The agency said it had some glitches that have primarily affected refunds for married couples filing joint returns.

“It’s been a real challenge for us,” said IRS spokesman Terry Lemons. “We know there is frustration out there. We understand, and we apologize.”

The processing issue is related to the form people must use to repay the credit — IRS Form 5405 “First-Time Homebuyer Credit and Repayment of the Credit.” The IRS had to pull returns of married taxpayers filing jointly who submitted their tax returns before Feb. 22. The agency had to process them manually, delaying refunds, Lemons said.

The slowdown in processing also affected taxpayers who received a credit and are now reporting the sale or disposition of their home. It also affected taxpayers who took the $7,500 credit and wanted to pay back more than the yearly amount required.

Lemons said the IRS is making adjustments to its processing systems and some of the affected returns started going out this week.

About 1 million households nationwide are expected to have to repay the $7,500 credit.

If you think your refund might be stuck in the holdup, you can check its status by going to www.irs.gov and using “Where’s My Refund?”

If you haven’t filed your return and you’re making a first-time home-buyer credit repayment, be sure to file correctly. You add the amount you have to repay to any other tax you owe on your federal tax return. This could result in additional tax or a reduced refund.

The IRS says couples filing a joint return for 2010 who received the credit on their jointly filed 2008 tax return need to file two 5405 forms, one for each taxpayer. For couples filing a joint return for 2010 but who had a different filing status in 2008, and thus only one spouse received the credit, the IRS recommends filing one form 5405 on behalf of the spouse who took the credit.

And this is yet another reason we need a simpler tax code.

Readers can write to Michelle Singletary at The Washington Post, 1150 15th St. NW, Washington, D.C. 20071. Her e-mail address is singletarym@washpost.com. Questions are welcomed, but because of the volume of mail, personal responses may not be possible.

(c) 2011, Washington Post Writers Group