“Service in the uniformed services” means the performance of duty on a voluntary or involuntary basis in a uniformed service, including [38 USC. § 4303(13) & (16)]:

• active duty and active duty for training,
• initial active duty for training,
• inactive duty training,
• full-time National Guard duty,
• absences from work for examinations to determine fitness for any of the above types of duty,
• funeral honors duty by National Guard or Reserve members, and
• certain duties performed by National Disaster Medical System, which is part of the Department of Health and Human Services, when activated for a public health emergency, and approved training to prepare for such service (added by Pub. L. 107-188, June 2002). See Title 42. U.S. Code, Section 300hh-11(d).

According to a Thompson Publishing Company’s Special Report, "Return from Duty, Return to Work: Understanding the Employer’s New USERRA Obligations" (2006), there is no exclusion for executive, managerial, or professional employees. The law even protects temporary, part-time, probationary, and seasonal employees, as well as employees on strike, layoff, or leave of absence. It does not, however, apply to individuals who act as independent contractors rather than as employees.

20 CFR, § Sec. 1002.18 provides that "an employer must not deny initial employment, reemployment, retention in employment, promotion, or any benefit of employment to an individual on the basis of his or her membership, application for membership, performance of service, application for service,or obligation for service in the uniformed services". The Act also prohibits employers from taking actions against an individual for any of the activities protected by the Act, whether or not he or she has performed service in the uniformed services. The Thompson Publishing Company Report also provides that it is illegal for an employer to “retaliate against someone who exercises his or her rights under USERRA”.

The law requires all affected civilian employees to provide their employers with advance notice (written or oral) of their military service orders. 32 CFR Part 104 was revised to provide that "although oral notice is allowed pursuant to USERRA, written notice of pending uniformed service provides documentary evidence that this basic prerequisite to retaining reemployment rights was fulfilled by the service member and serves to avoid unnecessary disputes". [32 CFR § 104.6(a)(2)(iii)(A)(2)]. Section (3) recommends that the advance notice be provided at least 30 days prior to departure.

The notice can also be provided by an “appropriate officer” of the Department of Defense. An "appropriate officer" is a commissioned, warrant, or non-commissioned officer authorized to give such notice by the military service concerned. No notice, however, is required if military necessity prevents giving advance notice or if giving notice is impossible or unreasonable. [38 USC. § 4312(a)(1)].

Employees may also need additional time off before starting military service. 20 CFR § Sec. 1002.74 of the regulations recognize that absences for military service may include a period of time between the date the employee leaves the job and the date the employee actually begins service. In addition, the Thompson Publishing Company Report suggests that “employees may need intermittent time off from work prior to military service for brief periods to put their affairs in order, for example, to interview child care providers, meet with bank officers regarding financial matters, or seek assistance for elderly parents”.

20 CFR § Sec. 1002.74 also suggests that the amount of time an employee may need to prepare for military service will vary. “Relevant factors include:

• the duration of the military service,
• the amount of notice given an employee called to military service, and
• the location of the service.”