Which document is essential for current military members or their spouses when applying?

The essential document for current military members or their spouses when applying is a copy of their military identification card. This card serves as a clear and official proof of military status, validating both the service member's current active duty status and their entitlements. In the context of applications, having a military ID can streamline the process by confirming eligibility for various programs or benefits that are specifically available to military personnel and their families.

The other options, while they may be useful in certain situations, do not offer the same level of direct relevance. A Social Security card is important for identification and tax purposes but does not verify military status. An employment verification letter is typically needed in job applications or for benefits that relate to employment, which may not be applicable in all scenarios. A letter of recommendation can support someone's application but is not a requirement for verifying military affiliation or benefits. Therefore, the military identification card is the most pertinent document in this context.