The "SSO tax" refers to vendors charging exorbitant prices for single sign-on (SSO) functionality, which is essential for security, but only available on expensive enterprise plans. This practice has become normalized, with many companies paying twice as much or more than they need to for SSO. The SSO tax is a form of "security tax" that traps individuals into paying for features they don't need, making it difficult for companies to adopt and maintain security best practices. Despite efforts to raise awareness about the issue through the SSO Wall of Shame, vendors have been able to continue charging high prices due to the low PR risk and the collective action problem of interconnected organizations relying on each other's security. To address this issue, potential compromises include offering cheaper ways to authenticate, charging less for SSO features, unbundling security from support and value-added features, or shifting industry norms towards a "buy vs. build" framework that prioritizes security by default.