Fax API for legal software

You are an engineer on a legal-software product (case management, e-filing, or records-request) with a ticket to make it send faxes. mintfax is a developer-first fax service you can test in a free sandbox before going live.

What your users send

Fax is still accepted or required in specific legal work, jurisdiction by jurisdiction. Users of legal software send:

Filings, where a court permits it. California’s Rules of Court carry Chapter 3 of Title 2, Division 3, “Filing and Service by Fax”, rules 2.300 through 2.306. Tennessee trial court clerks accept fax filings under Rule 5A of the Tennessee Rules of Civil Procedure.
Records requests to court clerks. The Broward County Clerk of Courts, for example, accepts records requests by fax today.

Which courts permit fax filing changes. Louisiana, for example, stopped accepting attorney fax filings on 2026-01-01. Build the workflow so your users can turn fax on or off per jurisdiction and per matter.

What the court rule requires of the sender

Where fax filing is available, the requirements come from the court’s rule, not from a fax vendor. Read the rule for each court, but expect items like:

A printed transmission record produced by the sending fax machine (for example California Rule of Court 2.304(d)).
A cover sheet in the form the court prescribes. California requires form MC-005 under Rule 2.304(b). Tennessee prescribes a Uniform Facsimile Filing Cover Sheet under Rule 5A.
Page limits set by the rule, which vary by jurisdiction.
The filer, not the fax provider, remains responsible for the filing. The clerk’s timestamp, not the sending machine’s, sets the filing time. No fax provider can establish a filing time; the timestamps mintfax records are evidence of transmission only.

What ABA guidance asks of the firm’s vendor choice

ABA Formal Opinion 477R, “Securing Communication of Protected Client Information”, applies a reasonable-efforts standard to how a lawyer sends client information. It does not endorse fax as a channel and does not prescribe specific security controls. It does ask lawyers to conduct due diligence on their vendors, including security policies, confidentiality terms, and an accessible forum for relief.

Formal Opinion 483 adds that a lawyer who suffers a data breach has a duty to notify the client under Model Rule 1.4. A firm buying your product will expect the integration to record enough for that reconstruction.

What mintfax provides for a sound integration

None of the capabilities below is required by any court rule or bar opinion. They are what makes the integration something a firm’s compliance reviewer can accept.

Proof of delivery. Every fax carries an attempt history: status, an error code from a public ten-code taxonomy, latency, and timestamps for each carrier attempt. GET /v1/faxes/{id} and GET /v1/events/{id} return the delivery record.
Signed webhooks. fax.delivered, fax.failed, and other status changes are signed with HMAC-SHA256 per the Standard Webhooks specification. See verify webhook signatures before writing to a user’s matter record.
Idempotent retries. Idempotency-Key is honoured on POST /v1/faxes for 24 hours. Retrying the same request returns the original response with Idempotent-Replayed: true; a reused key with a different body returns HTTP 409.
Audit export. The audit stream records content access, contractual acceptance, personnel access, and state-of-record transitions, with a linked SHA-256 hash chain you can verify offline. Export it as paginated JSON or CSV. See compliance.
Retention control. Fax content is kept for 90 days by default. You can choose a period between 7 and 365 days for each environment, or enable zero-footprint mode to delete content as soon as a fax is delivered or fails. The destination number and operational records remain. You can also delete a delivered or failed fax’s content through the API.
DPA. An authorized signer can review, accept, and download the DPA in the dashboard, on every account. See compliance for the agreement and its boundary.
Transport. TLS 1.2 or higher on both inbound API and outbound webhook delivery; plain-HTTP webhook endpoints are rejected at registration. See security.

What mintfax does not do

mintfax does not receive faxes. No inbound fax, no fax-to-email, no number porting, and no dedicated fax numbers.
No e-filing integration. mintfax sends faxes to a fax number. It does not connect to court e-filing systems, and it does not run service-of-process workflows.
No end-to-end encryption. The telephone network and the recipient’s fax equipment are outside mintfax’s control.
No SOC 2, HITRUST, ISO 27001, FedRAMP, or PCI DSS Level 1 certification.

The compliance page covers encryption, subprocessors, audit export, and the boundary of mintfax’s commitments. Other segment pages are on the For index.

Get started

Try the sandbox with the magic numbers to walk through delivered, busy, no-answer, and invalid-number cases before you send a real fax. The quickstart covers your first request. Pricing is per page.