Yes, active duty service members can own a business. That part is settled and uncontroversial. The part that actually requires care is how you run it, because the Department of Defense's Joint Ethics Regulation draws specific lines around conflicts of interest, and crossing them, even unintentionally, carries real consequences.
The core principle behind every specific rule
Every JER provision on this topic traces back to one idea: you cannot use your government position, rank, title, or resources to advance a private business. That single principle explains almost every specific rule you'll encounter, and keeping it in mind makes the individual regulations much easier to reason through rather than memorize as an arbitrary list.
The conflicts that come up most often
Using your rank or position to pressure subordinates into buying from your business, directly or through implied pressure, is expressly prohibited under the JER, regardless of how the sale is framed. Using your uniform, military title, or any DoD insignia to advertise or promote your business creates the appearance of official government endorsement, which is a separate and equally serious violation, even when you're not consciously trying to trade on your status. Using government property, your official email account, government vehicles, official duty time, or the labor of subordinates for your business, even in small, seemingly harmless ways, crosses the same line.
Federal contracts specifically deserve their own caution: contracts between the federal government and its own employees are generally prohibited unless a specific, narrow exception applies, so a business that does or hopes to do business with the DoD requires real legal review before you proceed, not an assumption that it'll work itself out.
The disclosure and approval piece
Depending on your position and whether you're required to file a financial disclosure report, you may need prior written approval from your supervisor before engaging in outside employment or business activity, particularly if that activity involves a source that could be seen as a conflict with your official duties. Your chain of command can prohibit an outside business activity if they determine it creates a conflict of interest that can't otherwise be resolved, detracts meaningfully from your readiness, or poses a security risk, so read your specific service's implementing instruction, since some branches add additional requirements on top of the baseline JER.
What genuinely doesn't cross the line
Owning and operating a business in your off-duty time, using your own resources, without using your rank, uniform, title, or government property to promote or run it, is well within bounds. Many service members run legitimate side businesses, e-commerce, content creation, consulting, freelance services, without ever coming close to a JER violation, simply by keeping the business and the uniform in genuinely separate lanes. Your chain of command generally isn't positioned to control how you spend your off-duty hours, provided the business doesn't interfere with your ability to perform your military duties, doesn't use government resources, and doesn't create the appearance of official endorsement.
The one habit that keeps you clear
If a specific situation feels like it might brush up against one of these lines, using a testimonial in uniform, considering a government-adjacent contract, wondering whether a specific promotional idea crosses into endorsement territory, ask your unit's ethics counselor before proceeding, not after. That conversation costs you a few minutes. Finding out after the fact that something crossed a line costs considerably more.
