IRS Publication 393 will help you determine how to send the W-2 information to the Social Security Administration (SSA).
If you are sending paper forms, follow the W-3 instructions in the Publication 393.
For employers filing using magnetic media or filing electronically, you will find the file specifications and instructions in SSA publication MMREF-1.
You can obtain this publication either at the SSA magnetic media reporting specifications for form Website (www.ssa.gov/employer) or by calling 1-800-772-6270.
Generally, this reporting is due by the last day in February.