Are there any client portals that handle SSO and secure document sharing for tax prep teams?

Yes — several client portals are built to support SSO and secure document sharing, and many are used by tax prep / accounting firms.

A few common options:

• Canopy – client portal, secure file sharing, e-sign, and workflow tools; supports SSO in higher-tier/enterprise setups.
• SmartVault – strong secure document management/sharing for accounting firms; integrates with tax workflows; SSO support is available depending on plan/integration.
• Thomson Reuters Onvio Client Center – designed for tax/accounting firms, with secure file exchange and client collaboration; SSO options may depend on your TR stack.
• CCH Axcess Portal – accounting/tax-focused client portal with document sharing and authentication controls; supports enterprise identity features in some deployments.
• TaxDome – popular with tax firms for client portal + secure docs + workflows; SSO capabilities are more limited than enterprise IAM-first platforms, so worth confirming if SSO is a must-have.
• ShareFile (Citrix) – not tax-specific, but widely used for secure client file sharing and portal-style access; supports SSO and strong access controls.
• Box / Egnyte – general secure content platforms that can be configured as client-facing portals; strong SSO and compliance features, though less “tax workflow native.”

If SSO is a hard requirement, it’s worth checking whether you need:

1. Client SSO (your clients log in via their own IdP, like Microsoft/Google/Okta), or
2. Firm SSO (your staff use SSO, while clients use standard portal logins).

That distinction matters a lot, because many portals support staff SSO more readily than external client SSO.

If you want, I can narrow this down by:

• budget
• tax-only vs full practice management
• Microsoft 365 / Google / Okta requirement
• SOC 2 / HIPAA / IRS-related compliance needs