Lol nah not official. But usually agreements stipulate if the person cheats or provides misleading information they face chances of being disqualified. But it also depend on the country and if you use the contest as a tax write off <img src="{SMILIES_PATH}/icon_e_wink.gif" alt=";)" title="Wink"> because technically the winner is obligated to pay taxes on winnings regardless in the US States. But you don't file a tax break how will they know <img src="{SMILIES_PATH}/icon_e_smile.gif" alt=":)" title="Smile"> that is what agreements usually stipulate any taxes is the responsibility of the winner. If you have rules to play then it's still technically an agreement that the entrant have to agree to go by. The example contest below limit only US residents are permitted to entering to minimize headache of worrying about other country laws.
Extracted from contest rules:
The potential winner will be required to complete, sign and return to Sponsor an Affidavit of Eligibility/Release of Liability (including, if legally permissible, a publicity release), an IRS form W-9 and any other documentation provided by Sponsor in connection with verification of the potential winner’s eligibility and confirmation of the releases and grant of rights set forth in these Official Rules, within ten days of attempted delivery of same. If a potential winner is a minor under the laws of his or her state of residency, Sponsor will have the right in its discretion to require the winner’s parent or legal guardian to sign the Affidavit of Eligibility/Release of Liability or to award the prize in the name of the winner’s parent or legal guardian (who will in such event be required to complete, sign and return an Affidavit of Eligibility/Release of Liability). The potential winner may also in Sponsor’s discretion be required to complete and return to Sponsor an IRS Form W-9 within 10 days of attempted delivery of same.
http://winit.intouchweekly.com/sweepsta ... 1736/rules
If it's a one time thing it probably could be snuck by but if it's a continuous thing you have to question is it worth the fines if you get caught.