E-signatures, built in.
Send a document for signature from inside your workspace. Route it to one signer or many, verify each signer's identity, and get the executed copy filed back automatically. No second tool, no copy and paste between apps.
4 documents
Signer 1 of 1
Daniel Park
d.park@acmecorp.com
Your fields
1 field to complete
Field 1 of 1
Not a checkbox feature. A defensible signature.
Routing, identity verification, and a tamper-evident certificate are the parts that turn a signed file into a record you can stand behind.
Recipients
Sarah Chen
s.chen@acmecorp.com
Needs a field
James Porter
j.porter@northwind.co
Needs a field
Signing order
Signer routing and ordering
Route a document to several signers at once, or in a strict order where each person signs only after the one before them. Set the sequence when you send it.
Identity check
Sarah Chen
s.chen@acmecorp.com
Verify it's you
We emailed a code to s·····@acmecorp.com.
Resend code (25s)
OTP identity verification
Before a signer can sign, they confirm a one-time passcode. The verification is tied to that signer and recorded against their signature, so you can show who actually signed.
Audit Certificate
CompletedService Agreement.pdf · Jun 23, 2026 23:09 UTC
Recipients (2)
Signer
Auth
Signed at
Sarah Chen
Jun 23 · 14:14
James Porter
Jun 23 · 16:08
Document fingerprint
SHA-256: a7f3b2c9d81e4f06b3...
Tamper-evident audit certificate
When the last signer finishes, Fastio generates an audit certificate that documents who signed, when they signed, and from where. Change the document and the record no longer matches.
Each signer's identity, captured alongside the one-time passcode check that confirmed them.
An exact timestamp for every signature, in the order the document moved through your signers.
The originating location of each signing event, recorded on the certificate that travels with the executed copy.
From draft to executed, in one place.
The document never leaves your workspace. Signing, identity checks, and filing all happen where the file already lives.
1. Prepare the document
Pick any document already in your workspace and choose to send it for signature. Place the signature fields where they belong. Nothing to upload again, nothing to re-create in a separate signing app.
2. Route it to your signers
Add one signer or several. Choose whether they sign in parallel or in a strict sequence where each person is only invited after the one before them has signed. You set the order when you send it.
3. Each signer verifies their identity
Before signing, each signer confirms a one-time passcode tied to them specifically. The record shows the person who signed actually proved they were there, not just that a link was opened.
4. Signers sign from a link
Your signers receive a link by email, open it in any browser, and sign. No Fastio account required, nothing to install. It works on any device. Every action is timestamped and captured in the audit record as it happens.
5. The executed copy files itself back
When the last signer finishes, the executed copy and its audit certificate return to the workspace automatically. No downloading a final PDF and dragging it into the right folder.
Chain of custody, end to end.
A signature is only as good as the trail behind it. Because signing happens inside the same workspace that stores the file, the request, every identity check, every signature, and the final filing all land in one append-only audit log. Nothing moves to an outside tool and comes back unaccounted for.
Identity-verified signatures and a tamper-evident certificate give regulated teams a record they can produce on request.
Send, sign, verify, and file are all written to the same append-only log, so the timeline of a document has no gaps.
The signed file returns to the right place automatically, so the version of record is never sitting in an inbox or a downloads folder.
See it inside a real workflow
In a law firm's matter intake, the client signs the engagement letter from a link, the executed copies file themselves into the matter folder, and every step lands in the audit log. Native signing is one step in that sequence.
Part of the same workspace, not a bolt-on.
Signing connects to the way you already share, collect, and approve documents in Fastio.
Sign from a link
Signers open a link and sign with no account to create, the same frictionless access you already use for sharing.
Explore sharingApprove, then sign
Route a document through internal sign-off first, then send the approved version out for signature without leaving the workspace.
Explore approvalsRun a matter end to end
See native signing inside a full legal matter workflow, from intake and engagement letters through filing.
See the legal workflow
Stop sending documents to a separate signing tool.
Send for signature, route your signers, verify their identity, and get the executed copy filed back, all inside the workspace where the document already lives. See the plans on the pricing page.