If organizations meet the following requirements, then the 990-N E-postcard is acceptable.
Small tax-exempt organizations generally are eligible to file Form 990-N to satisfy their annual reporting requirement if their annual gross receipts are normally $50,000 or less. Gross receipts are the total amounts the organization received from all sources during its annual accounting period, without subtracting any costs or expenses. Gross receipts are considered to be normally $50,000 or less if the organization has been in existence for 1 year or less and received, or donors have pledged to give, $75,000 or less during its first taxable year; has been in existence between 1 and 3 years and averaged $60,000 or less in gross receipts during each of its first two tax years; and is at least 3 years old and averaged $50,000 or less in gross receipts for the immediately preceding 3 tax years (including the year for which calculations are being made).