Delta vs Carl: practice management or clinical assistant?

Delta and Carl do not meet the same need. According to its website, Carl is "all-in-one" practice management software for therapists: calendar, online booking, video calls and invoicing, with a notes feature. Delta is a clinical assistant for mental health and allied health professionals: it transcribes what is said during the session, on HDS-certified infrastructure, which gives it a lot of context on each patient to write reports, keep the file up to date and produce long documents such as assessments and letters. Scheduling, appointment booking, video consultations and invoicing are coming to Delta: the OS plan, available for pre-order on our pricing page, announces scheduling, appointment booking and built-in invoicing.

What Carl does, according to its website

We read Carl's official website on 16 October 2026 (home page, FAQ and security page). Here is what it states. Everything below is according to its website; we have not tested the software.

Practice management software

According to its home page, Carl is "the all-in-one software designed for therapists". It targets support and mental health professions: psychologists, psychotherapists, hypnotherapists, sophrologists, speech therapists, naturopaths and, still according to its website, "more than 110 support professions". The website says Carl is developed between Paris and Barcelona.

Calendar, booking and video calls

• A calendar, synced with Google Calendar according to its FAQ.
• A booking page in your name, with your slots, session types, their length and their fee, according to its FAQ.
• Built-in video calls: according to its FAQ, the video link is created with the appointment.
• Appointment reminders.

Invoicing and activity tracking

• PDF invoices in one click.
• E-invoicing: according to its FAQ, invoices are put into the regulatory format and sent automatically through an approved platform (Super PDP).
• Automatic reminders for unpaid invoices.
• Activity tracking (statistics) and an accounting section.

Session notes with help from artificial intelligence

Carl also has a notes feature. According to its home page, you describe what happened "out loud or in writing", and Carl "turns your notes into a structured report". Its FAQ talks about dictation: many practitioners dictate from their phone between two sessions, and most describe their session in two to four minutes. Still according to its FAQ, Carl draws on the history of the follow-up, and you can edit the report, the summary and the part on the next session. The website states that its artificial intelligence remains an assistance tool and is not used to make a diagnosis. According to its website, the patient file brings together session history, observations and documents.

Carl is therefore first and foremost a practice management tool, complete on the admin side, with a notes feature built around dictation.

What Delta does

Delta is the clinical assistant for mental health and allied health professionals. Its strength is the clinical side, from the session itself to the assessment. For a full overview, see What is Delta?

Two ways to take notes

• During the session: Delta transcribes what is said.
• After the session: you dictate your observations.
• Either way, you can also add written notes.

A report and an up-to-date file

From these notes, Delta generates the session report: a short summary, a detailed summary and topics for the next session. It takes your profession and your approach into account (CBT, EMDR, psychodynamic, systemic…). It also updates the patient file, with a summary of the follow-up and the goals being tracked. You find the whole follow-up and how it has evolved in one place.

Letters, certificates and assessments

Delta also drafts letters, certificates and assessments, adapted to your profession. You will find examples in our clinical document templates.

A lot of context, long documents

When Delta transcribes the session, it has everything that was said, session after session. That context is what makes accurate reports possible, a file that truly follows how the patient is doing, and long documents such as an assessment or a letter to a colleague, without starting from scratch.

Scheduling and admin

Scheduling, appointment booking, video consultations and invoicing are coming to Delta: the OS plan, available for pre-order on our pricing page, announces scheduling, appointment booking and built-in invoicing. Delta does not do electronic claims submission, coding or test score calculation. It runs in the browser, with a Mac and Windows app that we recommend for sessions.

The differences, point by point

Type of tool

• Carl: practice management software with a notes feature, according to its website.
• Delta: clinical assistant, from transcribing the session to reports, the patient file and long documents.

Calendar, appointments and video calls

• Carl: yes, according to its website (calendar, booking page, reminders, video call link).
• Delta: scheduling, appointment booking and video consultations are coming with the OS plan, available for pre-order.

Invoicing

• Carl: yes, according to its website (PDF invoices, e-invoicing, reminders).
• Delta: built-in invoicing is planned in the OS plan, available for pre-order.

Note-taking

• Carl: voice dictation or written notes, according to its website. Its FAQ describes practitioners dictating between two sessions. Live transcription during the session is not described on its website.
• Delta: secure transcription during the session, or dictation after it, plus written notes.

Report and patient file

• Carl: a structured report, with a summary and a part on the next session, drawing on the history of the follow-up; a patient file bringing together session history, observations and documents, according to its website.
• Delta: short summary, detailed summary and topics for the next session, adapted to profession and approach; file updated with a summary of the follow-up and the goals.

Letters, certificates, assessments

• Carl: its website mentions a shared document library. Assisted drafting of letters or assessments is not described on its website.
• Delta: yes, including long documents such as assessments, adapted to the profession and informed by the context of the follow-up.

Health data and hosting

Both tools handle health data. Here is what each one states. To understand what the certification covers, see our guide to HDS-certified hosting.

Carl, according to its website

• Hosting: according to its FAQ, data is hosted by Scalingo, a "certified health data host (HDS), in the European Union". Its home page mentions "hosting in Europe". The exact country is not stated on its website.
• Encryption: according to its FAQ, data is "encrypted in transit and at rest". Its security page states that hosting is "100% in the European Union".
• Audio: according to its website, audio is deleted automatically once transcription is complete.
• Training: according to its website, data is never used to train an artificial intelligence model.
• Artificial intelligence processing: the provider and the country of processing are not stated on its website.
• Pseudonymisation: the term does not appear. Its website speaks of data "anonymised where possible" and suggests using the first name only or an internal identifier when this fits your practice.

Delta

• Data hosted in France by an HDS-certified host.
• Artificial intelligence processing in France.
• Patient name and identifying information pseudonymised before the artificial intelligence step.
• No audio file kept: audio is only used during the session to produce the transcription.
• Data never used to train a model.
• Data encrypted in transit and at rest.

On encryption, training and keeping audio, the two websites say similar things. Both state an HDS-certified host. The main difference is location: Delta states France for hosting and artificial intelligence processing, while Carl states the European Union for hosting and does not say where processing happens.

Pricing

Carl

According to its FAQ, read on 16 October 2026: a single plan, Carl Essentiel, at €29.90 per month including VAT, with no commitment. Free 30-day trial with no credit card. The website also mentions a 50% discount for the first months for practitioners who have been in practice for less than a year. This price includes scheduling, invoicing and notes.

Delta

According to Delta's pricing page, read on 16 October 2026 (prices including VAT):

• Free: €0/month, free forever, no credit card, 10 sessions per month.
• Pro: €35/month billed monthly with no commitment, or €29/month billed annually (€348/year). Unlimited sessions.
• 14-day Pro trial with no credit card.

The two prices do not cover exactly the same thing today. Delta Pro covers the clinical side, with transcription during the session. The OS plan, available for pre-order, adds scheduling, appointment booking and built-in invoicing.

What makes the difference

Transcription during the session

According to its website, Carl relies on dictation after the session, often a few minutes between two patients. Transcription during the session is not described there. Delta can securely transcribe what is said during the session: nothing important depends on your memory at the end of the day.

A real clinical assistant

• reports that take your profession and approach into account (CBT, EMDR, psychodynamic, systemic…);
• a patient file updated after every session, with a summary of the follow-up and the goals;
• letters, certificates and assessments drafted from the full context of the follow-up;
• data hosted and processed in France, pseudonymised before artificial intelligence.

And the admin side

Scheduling, appointment booking, video consultations and invoicing are coming to Delta with the OS plan. In the meantime, you can keep your current scheduling tool alongside Delta.

One place for the clinical file

We suggest keeping your clinical notes in one place, so you can find the whole follow-up and how it has evolved without searching through several tools. That is Delta's role: the session, the report, the file and the documents in one place. If you currently use a separate calendar, such as Doctolib or Google Calendar, Delta works alongside it, as we explain in Delta vs Doctolib. For a broader view, see our guide to software for therapists.

Frequently asked questions

Sources

• Carl, home page (in French), read on 16 October 2026.
• Carl, FAQ (in French), read on 16 October 2026.
• Carl, security (in French), read on 16 October 2026.
• What is Delta?, Delta reference page.