If you entered into the marriage in good faith and, have been living together as spouses, this final clean up step is nothing to be substantively concerned about. However, it is a BIG deal if the couple fails to file the I-751 within the prescribed 90 day period. If the two (2) year anniversary of the grant of permanent resident status passes without filing of the I-751, the alien spouse loses their permanent resident status and, becomes immediately deportable