Hello,
Thank you for posting your query.
In case you know as a matter of fact that the concerned person is working here, then you should not submit a false affidavit.
It is easy for the authorities to find out if a person is working here through just looking at financial transactions in a person's account. And giving a false affidavit in order to conceal information might land you in trouble. It will amount to creation of false document, concealing information from authorities, abetting unauthorized stay of a foreign national and cheating which is punishable under the law.
Regards,