Check, a startup building software tools for digitizing business payrolls, emerged from two years in stealth mode this morning with the announcement that it has raised $35 million in a fresh funding round.

The round was led by investments from Thrive Capital and the digital payments giant Stripe. No valuation for the startup was disclosed.

With this new round, the startup has raised a total of $44 million.

Stripe’s participation is notable, since Check is drawing from Stripe’s strategy of building payments infrastructure for the increasingly digital economy. While Stripe helps businesses to accept credit card payments online, Check is focused on connecting payroll systems with the fast-growing array of software tools for managing businesses. Check cofounder and CEO Andrew Brown, and much of his team, were previously behind the ebook startup Oyster, which was acquired by Google in 2015.

Check will be entering a fairly crowded field. Standalone payroll and HR software, such as ADP and Workday, is already widely used by enterprises. The digital payroll platform Gusto, founded in 2012, says it has 100,000 clients. And Square, which shares its focus on small business with Check, already offers payroll services that integrate with its sales and timesheet features.

But according to Brown, his company is focused on a niche not well-served by established players: making it easier for developers to integrate payroll features into a wider variety of software.

Many business software packages cater to specific categories of small business, such as plumbers, salons, or coffee shops. Some of these business management tools, such as the restaurant software Toast, already include payroll features. But Brown says the complexity of digitizing payroll, including the need to automate tax withholding for employees in various jurisdictions, makes building those features from the ground up too difficult and expensive for developers with smaller target markets.

“Imagine a yoga studio or a gym and the software that runs their business,” says Brown. “They have the ability to manage the number of people on staff, to book classes through the software, to accept payments from customers. But they can’t actually complete payroll, so they end up having to export that data and do it elsewhere.”

Check makes adding payroll to management software easier by handling its most challenging elements. In addition to tax calculations and transferring funds to the appropriate tax collectors, Brown says Check handles the filing of tax forms for services built using its system.

Most of Check's customers pay a flat fee per business user, plus a charge based on the number of employees being paid, Check said.

Using a broadly similar model for its online payments platform, Stripe has grown over the past decade into a private giant valued at as much as $100 billion. But by dollar volume, Check’s market is even bigger than Stripe’s. U.S. online credit and debit card payments, Stripe’s bread and butter, totaled $348.7 billion in 2019, according J.P. Morgan. Payroll, where Check is focused, is close to $9 trillion annual volume in the U.S., according to the Bureau of Labor Statistics, and a study by Stripe found that three out of four businesses use the sort of industry-specific management software its payroll tools are designed to work with.