Surprise! If you filed for the first homebuyer tax credit, the one Uncle Sam offered in 2008, you do have to pay it back.

Not, however, for the folks who took the later credits, offered in 2009 and 2010. They get to keep the money. That first round of tax breaks was considered a loan under the law.

Borrowers who got the credit for buying a home before April 8, 2008, now have to begin paying it back in installments, beginning this year.

Uncle Sam: You Owe Me

The good news is they have 15 years to make good on what is essentially an interest-free loan of up to $7,500. They can pay it back annually in equal installments, says the IRS. That’s a $500 tax hit each year.

The bad news is, yes, you have to pay it back. The IRS will be sending out letters to remind those folks.

The tax authority recommends that people adjust their withholding to account for the extra money, since an employer wouldn't realize it if you took the 2008 credit.

There are some factors to consider that can affect your liability, says the IRS:

• If you die, the loan is forgiven. If you file jointly and a spouse dies, the remaining spouse owes half the loan.

• If you stop using the home as your main home, for instance turning it into a vacation home or business location, the loan is due in full that year.

• If you sell, the loan is due in full that year. But, the repayment is limited to gains you made on the sale, assuming you sell to a non-relative. If you lost money or break even, you might owe less or nothing.

• If you transfer your home to a spouse (or former spouse in the case of divorce), that person is responsible for the payments.

Borrowers who waited got a better deal, up to $8,000 that won't have to be paid back if they stay in the home for 36 months.