SDVOSB eligibility comes down to four things: veteran status, a service-connected disability rating, ownership and control, and size. All four have to hold.
Veteran status and the disability line
You need to be a veteran with a discharge that was not dishonorable, which VetCert checks against your DD-214. Then comes the rule that actually separates SDVOSB from VOSB: at least one qualifying veteran owner needs a service-connected disability rating documented by the VA. This is a yes or no fact, not something an application can argue around, though there is no minimum rating percentage required, so do not rule yourself out over a low rating without checking current VetCert guidance. If you do not have a rated disability, you are not shut out of veteran contracting entirely; VOSB uses the same ownership and control rules without this requirement.
Ownership and control, checked separately
At least 51 percent of the business has to be owned and controlled by the qualifying veteran or veterans, and control means actually running the business, day to day and long term, not just holding the ownership stake. This is the same control standard SBA applies to every ownership-based certification, and it is where applications most often stumble, usually because a non-owner manager or a minority partner is the one actually calling the shots. This shows up most in businesses with a co-founder who is not a veteran, or a general manager who has effectively taken over daily decisions while the veteran owner stays hands off. If that describes your business, the ownership percentage on paper will not carry the application by itself.
Size, the same as everywhere else
You also have to be small under your primary NAICS code. Size standards vary a lot by industry code, so check the specific standard for your primary NAICS rather than assuming a number you have seen elsewhere still applies. If you have not checked your current standard, see size standards.
If the disability rule is the only one that fails
A veteran-owned business that clears ownership, control, and size but has no service-connected disability rating is not stuck outside veteran contracting. VOSB uses the exact same ownership and control test without the disability requirement, so the checking you just did against those rules still applies. The only thing that changes is which set-aside pool you can bid into.
If you qualify, what is next
Certification runs through SBA's VetCert system, at no cost. It is worth pursuing quickly if the VA buys what you sell, since the VA runs its own preference for veteran-owned firms on top of the government-wide set-aside rules. See which certification is worth your time if SDVOSB's facts do not quite match yours, since VOSB or another certification may fit better right now.