This really depends. There are provisions in regulations for temporary and short term off site placements by your employer. However, if the off site placement does not meet regulatory requirements a new LCA is required.
If there is a material change in your job then an amendment needs to be done. If the employer actually changes then a new H-1b must be filed.
However, this is all very general. You need to put on an appointment with your immigration lawyer to see what your situation requires. Good luck.
Amendment is to be filed for all material changes. If the position is the same, and there is a change in job location, new LCA suffices. However, if the client changes and accordingly some terms and conditions change, amendment should be filed.
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David provided a fantastic response - it really does depend - and you would be best served by running the specifics by your trusted immigration lawyer or other adviser to receive advice based on the specifics. Best of luck
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