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OnTask’s eSignature API: Enhance Your Application

An eSignature API built to fill the gaps in your application in minutes and get to market faster. 

An Electronic Signature API Your Way

Building secure, compliant, and legally binding eSignature capabilities into your software takes up valuable time and development resources.

Get that time back and avoid development headaches with a secure, proven API solution backed by the support, documentation, and resources of a software company with three decades of experience.

Get Started with Developer Resources


Free API Key

Grab your OnTask API key for free and start testing. No talking to sales, no credit card required.

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View our documentation to grab test code and learn more about OnTask API and its capabilities.

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Support Articles

View our support articles to learn about OnTask API and and how it can help enhance your application.

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Pay-as-you-go Pricing Per eSign

First 25 transactions / month

Free Tier

26-1000 transactions / month

$1.87 per transaction

1001-5000 transactions / month

$1.74 per transaction

5000+ transactions  / month

$1.49 per transaction

Discount and user-based pricing available. 

For advanced features such as custom workflows, custom SMTP, white labeling, embedding, and SMS please contact us.  

Case Study

HubSync Enhances Tax Preparation with OnTask API

“I think the combination of all that they bring to the table in a mature capacity is the reason to do business with them. They didn’t just invent something yesterday and hope it’s working. They have tried and true platforms and people who understand the business and how to make things work.”
John McGowan, CEO
Read More

Why Choose OnTask API?

  • 30+ Years in the Business
  • Quick Error Response
  • Robust Documentation
  • Support from Real Humans
  • Proven Reliability
  • Top-Notch Security

Do More with Our eSignature API


  • Add secure, compliant, legally binding signature functionality into your native forms and applications.


  • Embed dynamic digital forms into your applications or website for easy, simplified data collection.


  • Find and replace document fields,  generate documents from form data, and bulk send documents.


  • Automatically route forms and documents to the proper parties for signature, review, and completion.

Bring eSignatures Full Circle with Robust Workflows

OnTask API connects eSignatures with forms and workflows to bring you an end-to-end solution for automating processes.


Legally-binding eSignatures

Collect legally binding, HIPAA compliant eSignatures from any device.


Progress Tracking

Track signature status as documents flow through review.


Collect, Populate, & Generate Documents

Use digital forms to collect info from users to populate pre-existing documents or generate new ones.


Built-in Notifications

Automatically route documents to proper parties using emails and SMS texts.


Quick Integrations

Easily connect with thousands of apps using webhooks and in-app integrations.


Reusable Templates

Quickly automate processes by getting started with a pre-built template.

Built for Developers

Fast API Error Response

Consistent infrastructure monitoring with automatic reminders notify our team to minimize downtime and errors.

Clear Documentation

Concise, straightforward documentation for using and integrating OnTask API into applications.

Built to Last

 OnTask API is flexible to changing needs with easy editing and scalability as your business grows.

Maintains Backward Compatibility

As updates are made, backward compatibility is maintained to ensure continuous functionality.

Free API Key

Test the OnTask API key for free (No talking to sales, no credit card required).

OnTask API Business Benefits

Seamless User Experience
Integrate forms and signature features directly into applications to create a consistent user experience.

Unrivaled Support
Extensive documentation and proactive customer support help to overcome any implementation challenge.

Get to Market Faster
Save time and resources by incorporating proven functionality into applications rather than building from scratch.

Secure and Compliant
HIPAA, FERPA, SOC2, & CCPA compliant with legally binding signatures and electronic audit trails for enhanced security.

Get Started in Minutes
Integrate versatile forms, documents, and signature capabilities and start creating API calls in a matter of minutes.



  • OnTask API is HIPAA, FERPA, SOC 2, and CCPA compliant, and features a number of security features to protect data and combat downtime. Read about OnTask’s security and compliance.

  • OnTask API can be used for a wide variety of use cases, including but not limited to leasing packets, employee and client onboarding, proposals, quotes, questionnaires, and any other process using forms and documents.

  • OnTask API’s abilities include eSignature requests and collection on documents, document packet creation, automated document generation, document lifecycle management and storage, data collection through forms, automatic launching of workflows, as well as importing and exporting documents and data from other systems.

  • Our eSignature API comes with extensive documentation that allows developers to implement and launch within a matter of minutes. Support is available during and after implementation, as well as for more complex builds. Contact us to talk through your specific needs.

  • The purpose of an eSignature is to verify a document, while digital signatures also work to secure documents. OnTask utilizes both for a complete signature experience. Read more on the difference between eSignature and digital signature APIs.

  • An eSignature (electronic signature or digital signature) application programming interface (API) is a Representational State Transfer (REST) web service that allows subscribers to securely request signatures online, obtain status updates, and download the completed documents.

Have Questions About the eSignature API?