Next spring, the Census Bureau makes its once-a-decade count of the U.S. population. But scammers who just want to count your cash are already piggybacking on the event.

Although census workers conduct another survey each month, beware of anyone who comes to your door between now and next spring claiming to be gathering data for the 2010 census, says Census Bureau spokesman Derick Moore.

Here’s why:

Mailing of the official postage-paid census questionnaires begins in mid-March 2010. “Households that do not respond to that first mailing are sent a second questionnaire,” Moore says. “Only after they do not respond to the second do we send a census taker to their home.”

Those visits by one of the bureau’s 1.4 million census workers will occur in 2010 between April and July. Now that the bureau has completed its preparation fieldwork with workers who verified the nation’s 120 million addresses, citizens shouldn’t see any census workers at the door until then.

Already, some census-related scams have emerged. In rural Kentucky near the Tennessee border, “we’ve heard from several consumers who say that people identifying themselves as census workers come to their doors, ask a few census-type questions, and then solicit a donation,” says Kathleen Calligan of the Nashville Better Business Bureau. “They tell consumers they don’t get paid for their travel expenses and need gas money to conduct the census.”

And in the Midwest people have reported receiving a “2009 Census of Senior Citizens.” Sent by the self-styled Civic Council of Maryland, based in Frederick, it asks questions such as “Should the Death Tax be permanently repealed?” and “Should Medicare benefits be means tested?” The mailing asks that surveys be returned with a donation of up to $25.

Identity theft is another potential threat. “Our census takers will never ask personal or financial information such as your Social Security number, bank account information or credit card accounts,” explains Moore.

Other tips to distinguish census takers from fakers:

•  Legitimate census takers will wear this badge and carry a black canvas shoulder bag reading “U.S. Census Bureau.” The badge is not a photo ID but will contain the taker’s name and signature. So if you have doubts, ask to see a driver’s license or other photo identification to validate the taker’s identity.

• Any e-mail you receive purporting to be from the U.S. Census Bureau is a fake. Delete, without opening, any incoming e-mails alleged to be from the Census Bureau, as they may contain harmful spyware.

• Census workers will never solicit donations or other types of payment.

• To verify when home visits will be made in your area, or to report suspicious census-related activity, call your local Census Bureau office.

Sid Kirchheimer is the author of Scam-Proof Your Life (AARP Books/Sterling).