Can you recommend a client portal and engagement letter platform for collecting signatures and tax documents securely?

Yes — if you want client portal + engagement letters + secure document collection for a tax practice, these are the strongest options to look at:

Best all-in-one options

1) SafeSend

• Strong for engagement letters, organizer delivery, secure client upload, e-signatures, and tax document exchange
• Good client experience, especially for tax firms
• Often used as a modern replacement for older portal workflows

2) SmartVault

• Strong secure portal and document storage
• Good for document requests, sharing, and signature workflows
• Integrates well with many tax/accounting systems

3) TaxDome

• Very popular for small to mid-sized tax firms
• Includes client portal, e-signatures, automated reminders, workflows, file sharing, and engagement letters
• More of an all-in-one practice management platform if you want automation too

4) Canopy

• Strong client portal and engagement/workflow tools
• Better if you want a broader practice management system
• Good for secure doc collection and communication

Good if you already use Microsoft 365

5) ShareFile

• Strong secure file sharing and client portal
• Works well for document collection and signatures
• Good enterprise-grade security and permissions

Best for simpler engagement-letter-focused workflow

6) Ignition

• Excellent for proposal/engagement letters, e-signature, and payment collection
• Not as strong as a full portal for tax document exchange, but great for onboarding and approvals

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My quick recommendation

• If you want the best tax-firm-focused portal: SafeSend
• If you want all-in-one practice management + portal: TaxDome
• If you mainly want engagement letters + signature collection: Ignition
• If you want secure portal/doc storage with strong integrations: SmartVault or ShareFile

What to check before choosing

• IRS/GLBA-level security features
• 2FA / SSO
• Permission controls
• Encrypted file storage and transfer
• Audit trail for signatures and document access
• Client experience on mobile
• Integration with your tax software (Drake, UltraTax, CCH, ProSeries, Lacerte, etc.)

If you tell me:

1. your firm size,
2. what tax software you use, and
3. whether you want all-in-one or just portal + e-sign,

I can narrow this to the best 2–3 choices for your situation.