What exactly is an invoicing API? If you're handling invoices manually or using outdated systems, you're likely wasting time, risking compliance issues, and missing automation opportunities.

In this blog, we break down what invoicing APIs actually do, how they integrate into your system, how invoices are created and sent through them, and how they handle different country regulations—so you can decide if it’s the right move for your business.

How Invoicing APIs Work

How to integrate Invoicing API

How Invoicing API Creates an Invoice

How Does Invoice Sending And Receiving Work?

Country Regulations

 

 

How Invoicing APIs Work

An invoicing API is designed to streamline the entire invoicing lifecycle: from creating the invoice, checking for compliance, sending and receiving it, to processing payments and archiving it for tax audits. It supports e-invoicing, a more convenient, and cost-effective approach to invoicing.

Here’s how it typically works:

Integration: Your developers connect your application to the API via standard HTTP methods (POST, GET, PUT, DELETE).

Create Invoices: When a customer makes a purchase or completes a transaction, your system sends relevant data (such as buyer details, items, and prices) to the API. In return, it generates a valid invoice.

Send Invoices: The API can automatically email the invoice to the client or return a PDF version for download.

Track & Manage: Use the API to monitor payment status, cancel invoices, issue credit notes, or send payment reminders.

Compliance: Most invoicing APIs support country-specific regulations like digital signatures, e-invoicing standards like Peppol, and currency conversion, helping your business stay globally compliant.

 

 

How to integrate Invoicing API

The first step is to assess your business needs, as not all invoicing APIs are built for the same type of companies or use cases. Some APIs are designed for local markets and better suited for small businesses, while others offer only basic functionality, best for companies that send a limited number of invoices per month. On the other end, there are robust, feature-rich APIs built for large, global enterprises.

This decision affects everything: pricing models, integration complexity, and how well the solution will scale as your business grows. Once you’ve chosen a provider, every invoicing API includes technical documentation. Pay close attention to these key sections:

Authentication

Creating Customers

Creating Invoices

Sending Invoices

Webhooks (for real-time updates such as payment status)

Depending on the provider, top-tier APIs can typically be integrated in under a week with one or two developers. Many also support self-onboarding, allowing you to sign up and start testing instantly. Still, speaking with their sales or technical team is usually a good idea, as they can help clarify use cases and point you to the right features.

If you intend to offer the invoicing feature to your clients as part of your platform, make sure it supports white-labelling and, most importantly, multitenancy. We’ll cover them in more detail later.

 

 

How Invoicing API Creates an Invoice

An action has to happen first, which can either automatically online, with payment recieved for an ecommerce profudct, or you do it manually. The software sends a POST request to the API’s /invoices endpoint. This request includes:

The API has to process all the main data, but the scale and which depends on each country's regulations, but in general it processes:

If all is correct, it creates the invoice in its database and optionally:

Response example:

 

 

How Does Invoice Sending And Receiving Work?

After an invoice is created, the API performs an additional compliance check to ensure it meets the latest regulatory standards. The invoice is then stored according to the legal requirements of the relevant country, including specific timelines and formats for archiving. Once stored, the API returns an invoice_id, which can be used for further actions.

To send the invoice, you typically trigger a request like:

POST /invoices/{id}/send

You can track the status using:

GET /invoices/{id} → Returns whether the invoice is sent, viewed, or paid

Some APIs also support webhooks, providing real-time status updates without polling

If an e-invoice is sent, it usually enters the Peppol Network, where it can be reviewed in real time by the government. It’s validated, approved, and may even receive an official stamp. The invoice is then delivered to the recipient’s invoicing software or API.

It’s important to note: not all APIs support e-invoicing. If government mandates are not in place, the format must be agreed upon beforehand. Once the recipient’s software receives the invoice, it validates and approves it. If automated workflows are enabled, the invoice is then archived and paid.

Here is an example of sending a simple invoice.

 

 

How Multitenancy Works For Invoicing APIs

Multitenancy is essential for B2B SaaS platforms, neobanks, and other platform-based businesses that offer business solutions for their clients. It enables multiple companies (tenants) to use the same invoicing infrastructure while maintaining full data isolation—including branding, customer information, and transaction details.

Here’s how multitenancy typically works:

Each user has a unique account or “tenant ID”

Data isolation at the database level

Custom branding per tenant

Shared endpoints, isolated data

 

 

Additional Invoicing API Features For Specific Use Cases

APIs can vary widely in what they support, so it's important to align capabilities with your business needs from the start.

For example:

Do you operate in multiple countries? You’ll need an API with global compliance support—so you’re not forced to switch providers later.

Do you accept cryptocurrency? Then your API must handle crypto payment logic, including conversion to local currency and proper invoice formatting.

Need automatic payments or the option to generate human-readable PDFs from e-invoices? Not all APIs can do that.

Before you integrate, clearly define your requirements and confirm the API covers them—so you avoid time-wasting or roadblocks down the line.

 

 

Integrate Invoicing API With Space Invoices In Less Than A Week

Space Invoices is a modern invoicing API built for SaaS, neobanks, fintech, e-commerce, and platform-based SMBs. We provide comprehensive developer documentation and fair, transparent pricing designed to grow with your business.

With Space Invoices, you can:

Use one API for current and future global tax and invoicing compliance

Support and upsell clients worldwide

Ensure compliant archiving and reporting to local tax authorities

Position yourself as a one-stop shop for your users

Automate workflows, eliminate errors, and reduce operational costs

Have questions about integrating invoicing into your product?

We’re ready to help.

Additional reading:

• 2030 Intra Community E-invoicing Mandatory EU ViDA
• 3 Best White-Label Invoicing APIs for B2B SaaS, Fintech, and Neobank Platforms
• Can I issue an invoice without GST New Zealand