Our petition was approved. What do we have to keep doing as the employer?

Treat immigration compliance as a continuous system rather than a set of finished filings. Form I-9 must be completed within three business days of hire, and enforcement now classifies many I-9 errors as substantive violations that cannot be cured once discovered — missing or wrong dates, incomplete Section 2 attestations and missing preparer information are the common ones. USCIS has also signalled it will look back at prior filings, so H-1B, L-1, PERM and green card cases for the same worker need to tell one consistent story.