HelpPls:
While you are correct that the checks provided written proof that you received the money, this money is not reported to the IRS with your name and SSN attached to it. Hence, the IRS has no way of knowing your received the money. That is what I meant by an audit trail.
As for checking your bank records, the IRS neither the time, manpower or inclination to randomly check taxpayer's bank accounts in hope of finding extra income. They only do so when they receive information that leads them to believe they will find something worth investigating.
Oormi:
You will file normal (Form 1040/1040A/1040EZ) tax returns for 2005 instead of the non-resident return (Form 1040NR/1040NR-EZ).
You will be able to claim the standard deduction on the normal returns, or you can itemize if your itemized deductions exceed your stamdard deduction (not likely unless you have purchase a home and are making mortgage payments and paying real estate taxes).
It is possible that your employer, being aware that your visa status has changed, may issue you two separate W-2s, one for your F-1visa status and the other for your H-1 visa status. However, if only one W-2 is prodiced, go ahead and file the normal tax return.
The W-2 should show a shortfall in withholding for Social Security and Medicare taxes (I assume you did not have Social Security and Medicare taxes withheld while you were on F-1 visa status), but it is likely that the IRS will not even notice (they tend to focus on the income tax portion of the W-2). If they do notice, they will contact you and you can then explain your new visa status.