Some travel carriers (airlines and cruise lines) do not require this form at all. Some do. Check with your carrier early! Of those that do, some only require the form be signed by your accredited veterinarian. Some travel carriers (airlines and cruise lines) only require the form be signed by your accredited veterinarian. That is the case with Cunard. However, some also require that the form be endorsed by the USDA!
To receive endorsement by the USDA, the original form needs to be delivered to the central USDA office in your state - in California, with a $37.00 check (or credit card fee). They will endorse this and return the original to you if you include a return envelope. If you need your paperwork returned sooner (which most people do), include a pre-addressed FedEx overnight envelope with your paperwork. The USDA typically will stamp documents on the same day or the following day after they receive them.