You probably do not need to file an amendment petition if your job duties do not change.
This answer is of a general nature and should not be relied upon as final, nor is it intended as legal advice. Consult with a qualified attorney before making any legal decisions. Gen Kimura, (832) 247-6932.
At a minimum, you employer needs to have a valid LCA for the new location.
Your employer really should retain an experienced immigration lawyer to review all the facts, advise you, and handle the case.
J Charles Ferrari Eng & Nishimura 213.622.2255 The statement above is general in nature and does not constitute legal advice, as not all the facts are known. You should retain an attorney to review all the facts specific to your case in order to receive advise specific to your case. The statement above does not create an attorney/client relationship. Answers on Avvo can only be general ones, as specific answers would require knowledge of all the facts. As such, they may or may not apply to the question.
There are no provisions to amend LCAs. You will need to file a new H1-B petition with that new LCA.
The same $1500/$750 fee that your employer originally paid ($750/employee if the employer has less than 25 full-time quivalent employees) will likely apply. Your employer will probably not need to pay the $500 fraud fee because you are not changing employers.
You should check to see whether your employer already has an LCA for the new worksite. If your employer already has that LCA, then your transfer to that worksite may not require an amended petition.
This is a general answer and does is not intended as final or legal advice. Please consult an immigration attorney to review the specific facts of your case.