Looking at the Final Guide 2013 page 67, I find “If income is less than $25,000 a year, you will not have to file again until revenue goes over that amount, but you will have to file the initial return to let the IRS know that. Failure to file the return may cause your exemption status to be revoked.” This suggests you can file an initial 990 and not file again. It should be clear that a 990N must be filed annually. See next para in the Guide. Also the $25 thou figure should be $50 thou.