About LSAT and LSDAS Registration
You must register in advance for the LSAT. Online registration through the LSAC website is the preferred method, although you can register instead using a printed form available at the LSAC website and in the printed LSAT/LSDAS Registration and Information Book (published annually).
The LSDAS (Law School Data Assembly Service) is operated by LSAC and functions as an information clearinghouse for the law-school admission process. The LSDAS collects your undergraduate transcripts and LSAT score reports, and then creates a standard-form report that it provides to the law schools.
LSDAS registration is not optional. Registration is for one year only, which means that you must register for the service during the year you are applying for admission. If you register but then decide not to apply for admission until a later year, you'll need to register for the service again for that year.