How to Choose the Right HR & Payroll Integration Partner [Free Buyer’s Guide]

If your business serves employers through software or services, chances are HR and payroll data is mission-critical. But accessing that data efficiently and securely across a fragmented landscape of systems is a serious technical challenge.

Historically, companies have relied on manual SFTP file transfers or built API integrations in house, both of which are resource-heavy and difficult to scale. Today, a new category of connectivity solutions — unified payroll APIs — is gaining momentum as a more efficient, flexible, and scalable alternative.

Still, not all HR and payroll integration vendors are created equal. Whether you're aiming to accelerate time-to-market, reduce engineering overhead, or unlock new revenue streams, the vendor you choose will have a direct impact on your bottom line.

In this HRIS and payroll API integration guide, we’ll walk through the four essential buying criteria to consider when comparing payroll integration vendors and how to make the smartest investment for your business.

The 4 buying considerations for HR & payroll APIs

When you’re comparing HR and payroll integration vendors, it’s easy to get lost in feature lists and technical specs. Instead, anchor your evaluation around these four pillars. Each one speaks to a critical function of scalable, secure HR and payroll connectivity:

• System coverage
• Employer experience
• Domain expertise
• Security + scale

Let’s break each one down.

1. System coverage: How broad is their integration network?

System coverage is the first and most foundational question to ask. Your integration partner should support both market-leading HRIS and payroll systems (think ADP, QuickBooks, Gusto, and Paychex) as well as long-tail providers that still power a significant percentage of employers.

The payroll market is notoriously fragmented: the top 10 providers only cover 61% of employers in the U.S. To capture the remaining market, your vendor needs to support hundreds of additional systems, including platforms that don’t offer an API.

Look for a provider that not only supports API-based integrations, but also offers workarounds for non-API systems, like automated scripts or tech-assisted data access methods. Bonus points if they have formal partnerships with major providers, as that typically improves connection reliability, uptime, and data access.

2. Employer experience: How easy is onboarding and adoption?

A technically sound integration is meaningless if your customers can't (or won’t) use it.

A strong employer experience means:

• Fast, self-serve onboarding
• No CSV uploads or SFTP setup
• Clear connection progress tracking
• No third-party contracts or paywalls

The best vendors make the integration process virtually invisible to your end users, enabling authentication and data sharing in minutes instead of days (or weeks). This leads to faster onboarding, a lower support burden for your team, and ultimately higher conversion and retention rates.

Also watch out for billing models: some vendors charge employers directly, which can introduce friction and slow adoption. Opt for vendors that charge your business directly, not the customer. This comes with more flexibility — you can opt to absorb the cost, pass it on to the user, or upsell connections as an add-on — and can come with additional benefits like volume-based discounts.In every scenario, it's more efficient than asking the vendor to collect payment from employers directly and avoids forcing your customers to sign an agreement with a third party.

3. Domain expertise: Can they handle your use case with depth?

There are generalist API aggregators, and there are specialists that focus heavily in one domain. Generalists tend to support a wide range of data categories, but the trade-off is that their depth within a specific domain is limited. Niche providers, on the other hand, invest heavily in mastering a single category (like HRIS), so they’re able to invest in deeper partnerships and support more granular data access for those providers. 

If your use case requires specific data (like detailed pay statement line items) or the ability to write changes back to the source system, go with a provider that specializes in HRIS and payroll systems.

Ask about:

• Coverage within your domain of interest
• Industry partnerships
• Supported data fields (e.g., employment status, compensation, benefits)
• Write-back capabilities, like creating or updating payroll deductions
• Experience with edge cases unique to employment data
• Data standardization across providers

This last bullet is especially critical in the employment space, where there is little to no standardization in naming conventions and data structures. If the provider you choose doesn’t standardize data into a unified format, you’ll likely need to dedicate a portion of your Operations team to normalize the data you receive, or build an in-house tool to automate this work.

Domain expertise also ensures better support, faster troubleshooting, and a platform built specifically for the complexities of employer systems — not just generic data syncs.

4. Security + scale: Is the infrastructure enterprise-ready?

Payroll and HR data is some of the most sensitive data your application will handle. These systems hold personally identifiable information (PII) like social security numbers (SSN), bank account numbers, compensation data, and more. Your integration vendor must meet strict standards for security, compliance, and scalability.

Look for:

• SOC 2 Type II, GDPR, HIPAA, and CCPA compliance
• End-to-end encryption in transit and at rest (TLS 1.2+, AES 256-bit)
• Secure authentication protocols like OAuth and API tokens
• 24/7 monitoring and incident response
• Data access controls to limit liability

Equally important is the vendor’s ability to scale with your business — including infrastructure to navigate provider rate limits, maintain high uptime (99.9%+), and support thousands of concurrent employer connections without degradation.

How to quantify the ROI of HR & payroll APIs

One of the strongest cases for investing in a unified payroll API is the multi-dimensional ROI it can deliver — often far beyond what internal teams initially estimate.

Here’s how a well-chosen HR and payroll integration partner can move the needle:

• Unlock new revenue by supporting previously inaccessible systems or closing more deals faster
• Accelerate onboarding and reduce manual data entry, shortening time-to-value
• Cut engineering costs by eliminating the need to build and maintain dozens of custom integrations
• Improve retention by enabling stickier product experiences via embedded employment data
• Free up your team to focus on core product innovation instead of ongoing integration maintenance

Companies using prebuilt payroll integration solutions have reported a 67% increase in average deal size, engineering cost savings north of $1M annually, customer onboarding that takes under a minute, and faster access to key provider partnerships. 

By attaching real dollar values to outcomes like these, you’ll be able to make a strong internal case for investing in your chosen solution and ensure the investment gets prioritized.

Download the full HRIS and payroll API integration guide

If you're serious about comparing payroll integration vendors and choosing the right partner for your business, don’t start from scratch.

Download our free Buyer’s Guide to HR & Payroll Integrations to get:

• A more detailed breakdown of the 4 buying pillars
• Specific evaluation criteria and a customizable RFP template
• Real-world benchmarks from companies using connectivity solutions today

Get the guide (+ free RFP template) → 

Whether you're expanding your provider coverage, optimizing onboarding, or looking to improve operational efficiency, this guide will help you make a high-confidence decision and turn your integration strategy into a competitive advantage.