Hello hope this message finds you well. If you are going to file an L visa you must file it with USCIS first and once the visa is approved then you could do consulate processing to get your passport stamped if the beneficiary is outside of the US. However, I recommend that before you file anything that you have a consult with an attorney to determine if this is your best option. There might be better options for you. Best of luck!
The USCIS will first approve an L1A petition filed by the qualifying U.S. employer. You will then apply for an L1A visa at a U.S. Consulate.
For a new office situation, the approval is likely to be for one year, and the visa that is issued by the Consulate will normally match this length but will never exceed it. Consult with your current immigration attorney for case specific advice.
The information contained in this answer is provided for informational purposes only, and should not be construed as legal advice on any subject matter, nor should it be viewed as establishing an attorney client relationship of any kind.
Your L1-A would have to be applied first as a petition with the USCIS. Once approved you will have to obtain a visa through the US consulate in tokyo. In our experience, consulate interviews are very grilling in L1-A cases, so please be prepared to answer all questions that would come up, especially depending on the type and nature of business, finances of your business (tax returns, client invoices, etc), future projections of your new office in the US, and financial viability of the same. Also, it is always better to have a list of prospective US clients and some engagement letters with them which can strengthen your case. It is advisable to retain a competent immigration attorney who specializes in L1 Cases.
I think the U.S. based company must initiate that L1 submission properly for your subsequent consular application.
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