Do I need a new USDOT number if I am changing my company’s Legal Name or Form of Business?

No.

USDOT numbers are not transferable and are assigned to only one person and remain assigned to that person forever.  A person includes an individual, corporation, partnership, or other business organization as authorized by state law.  Each separate and distinct person must have separate registration.

For corporations, partnerships and other business organizations, the USDOT number will remain the same when there is a change in company officials, address or other demographic information, and the corporation, partnership, or other business organization will continue operations as the same legal person/entity. In case of a change in demographic information, the motor carrier is required to file an updated Form MCS-150, Motor Carrier Identification Report, within 30 days of the change.  

A change in the FEIN WILL generally result in a new DOT number.

Source: Maryland Motor Truck Association