When you renew your passport, you are now required to list your social security number which is sent to the IRS. It is not known at this time what the IRS is going to do with this data, but there is a good chance they will be checking for Citizens and residents living abroad who have failed to file there yearly income tax return with the IRS.
Also, now when applying for citizenship or bringing a new nonresident spouse or children back to the U.S. after living abroad, the immigration people are asking for proof that the past years tax returns have been filed.
Remember if you are required to file tax returns, you must file the return for each, or the statute of limitations for the IRS to assess taxes, etc. never runs out.
