The IRS does not require you to enter your A-Number for the filing of your Tax Return. You have been issued a Social Security Number so this is how the IRS identifies you and your immigration status.
Your immigration status is not relevant on the same level as is with other Federal Agencies. In the case that you were a Resident Alien but did not have a visa you would be required to request an Individual Taxpayer Identification Number (ITIN) in order to file a Tax Return.
For a quick read regarding this issue please follow the link to the article below:
https://turbotax.intuit.com/tax-tools/tax-tips/General-Tax-Tips/Tax-Tips-for-Resident-and-Non-Reside...
