What is an invoicing API? Here’s what you need to know

Accessing accurate and timely invoicing data from your accounting system or from customers’ can benefit your other internal applications or your product in a variety of ways. 

These benefits include anything from sending invoices on time to recognizing revenue correctly to powering insightful dashboards.

To help you reap the full benefits of invoicing integrations, we’ll break down what an invoicing API is, real-world examples, and integrations worth building.

Invoicing API definition

It’s any endpoint(s) that lets you access and perform actions on specific invoicing data, whether that’s retrieving, posting, deleting, or updating specific invoicing records. 

Related: What is accounting integration?

Invoicing API examples

The specific invoicing data you can access and the actions you’re able to perform on specific invoicing fields largely depends on the API provider you use. 

We’ll break down how these differences look across different accounting systems.


The widely-used enterprise resource planning (ERP) system lets you get, post, update, and remove any number of invoice records.

You can also take additional actions. For instance, you can transform an invoice into a “creditMemo” when POSTing it into a system, allowing you to remedy inaccurate invoices, process returns successfully, and more. 

In addition, you can transform an invoice into a “customerPayment” via a POST request. This can be helpful when invoices and payments occur simultaneously, as it allows you to immediately recognize the revenue and minimize invoice entries.

NetSuite API documentation on invoices
NetSuite’s API documentation covers all of the invoicing endpoints you can access, along with the details associated with calling each

Related: Payroll integration examples


Xero, an online accounting software, offers similar capabilities to NetSuite’s invoicing API; you can create, update, and delete specific invoices or all of the invoices in a variety of ways.

There are also a few more powerful capabilities worth calling out:

  • Make a POST request to trigger an email to a customer with the invoice
  • Use a GET request to find the history of changes made to an invoice
  • Construct a PUT request to add specific notes to an invoice
  • Leverage webhooks to receive real-time notifications when an invoice gets created or updated

Learn more about Xero’s invoicing API.

Sage Intacct

Sage Intacct is a financial management and services company that lets you retrieve, list, create, update, and delete invoices.

Sage Intacct documentation on invoices
Sage Intacct’s API documentation includes all of their invoicing endpoints above the fold, helping you navigate to the relevant section quickly

Sage Intacct’s invoicing endpoints offer a variety of functionalities. Here are just a few highlights:

  • Reverse invoices to how they looked in a particular time period in the past, such as a week ago
  • Get PDF versions of specific invoices
  • Query invoices by specific filters, like date range, invoice amount, customer type, and more to only access a certain set of invoices

Invoicing API use cases

To help you use invoicing APIs effectively, we’ll break down a few internal and customer-facing use cases worth implementing.

Integrate your CRM with your accounting system to streamline invoice creations and sends

Once you close a new customer, your team will want to move quickly on invoicing them. 

To help facilitate this, you can connect your CRM with your accounting system and build a sync where once an opportunity is marked as “Closed-won” in the former, the associated account gets created in the latter. 

Salesforce and NetSuite sync

Specific fields, like due date, amount due, and contact information can also be populated for that account in the accounting system automatically, enabling your finance team to create and deliver an invoice quickly.

Related: Financial API integration use cases

Sync your accounting system with your business intelligence platform to power actionable reports

Invoicing data, paired with other types of data, can help your analysts assess business performance, uncover trends in performance, and make predictions for the coming quarters and years—all through their BI tool of choice. 

To help your analysts access and use invoicing data successfully in their BI platform, you can integrate your accounting tool with your BI solution and implement a sync that allows invoicing-specific data to automatically get added to predefined BI reports.

Xero and Tableau sync

Connect your e-signature platform with customers’ accounting systems to help them create invoices faster

Say you offer an e-signature platform—like DocuSign—that allows users to create and send documents to customers.

To help customers create invoices accurately, quickly, and easily, you can connect your product with customers' accounting systems and build a sync where once a contract is fully-executed in your platform, a customer account gets created in the associated customer’s accounting system and the contract gets uploaded to the account.

Customer-facing sync for fully-executed contracts

Sync your financial planning tool with customers’ accounting systems to create and populate models quickly

Imagine you offer a platform that helps customers build and manage a range of financial models (e.g., sales forecasts) that help them make critical business decisions.

To enable users to realize a faster time to value and generate more accurate models, you can offer integrations with customers’ accounting systems to sync invoicing data, among other types of data. Once the data begins to sync, your product can automatically create and populate certain models on customers' behalves automatically. 

Sync for feeding customers' invoicing data to your platform

Related: A guide to accounting API integrations

Sync customers’ invoicing data with your product by leveraging Merge

Merge, the leading unified API solution, lets you access more than a dozen accounting integrations through a single build, letting your product access and sync all of your customers’ invoicing data—among other types of financial data.

Merge's accounting integrations
A snapshot of the accounting integrations Merge supports through its Accounting Unified API

Merge also provides Integration Observability features that let your customer-facing teams manage your integrations; advanced features to access and sync custom objects and fields; and integration maintenance support through its team of partner engineers.

You can learn more about syncing invoicing data with your product via Merge by scheduling a demo with one of our integration experts.