As noted above, while petitioners should do their best to disclose in advance all proposed activities, they may add or subtract performances involving similar services without filing a new petition, provided the new activities take place within the classification period and on behalf of or in association with the same petitioner. Indeed, provided activities of the type described in the petition actually occur, it is not material that the specific activities themselves do not take place, assuming, of course, that the petitioner initially included them in good faith.

What constitutes "similar" services is a matter of U.S. Citizenship and Immigration Services (USCIS) discretion. An O-1B concert hall soloist can add engagements in concert hall venues without concern, and most likely dates in smaller, more commercial or academic venues as well. It would probably be acceptable to USCIS were the soloist to play different music, jazz instead of classical, for instance, on those added dates. The soloist would still be playing his or her instrument, before a live audience attracted because of the soloist's reputation with that instrument, even though the soloist's O-1B reputation was gained by performing classical music only. It is less clear whether that soloist could add dates to perform as a member of a jazz ensemble. And it is debatable whether that soloist could add studio recording dates without additional action.

Where the artist's or group's principal purpose for being in the U.S. has materially changed, the petitioner must file an amended petition. An amended petition in this case simply means that the petitioner will check off Box 2c ("Change in previously approved employment"), in Part 2 of the I-129 petition, and also request an extension of stay (Part 2, Box4c). Otherwise, the petition substance and process would remain the same.

Note that if added or future engagements will take place in conjunction with another employer or agent altogether, that party must file a separate petition, unless the original petitioner filed an itinerary-based petition, including a cover letter that allowed for additional engagements to be added. For example, if an artist changes management companies mid-stream, the new management will need to file its own petition. This, of course, would not be an amendment.