The US employer must file the initial L-1 petition with the USCIS. This petition includes Form I-129 plus the L supplement along with the various supporting documents mentioned above, along with a filing fee of $460. The free must be paid by by check or by a money order drawn on a financial institution located in the US and payable in US dollars. The instrument must be made out to the “Department of Homeland Security.”
Once this package is mailed to the USCIS, you must wait for two notices (i) the Acceptance Notice, proving that the USCIS has filed your application; and (hopefully) (ii) the Approval Notice, notifying you that the USCIS has accepted your application. Once you are in L-1 status, however, be aware that if you leave the US, you will need an L visa issued by a US embassy or consulate to re-enter the US (except for certain limited excursions to Canada or Mexico).
If you are located abroad at the time your I-129 is accepted by the USCIS, you will still need to obtain an immigraiton visa to enter the US (see below).