Simple, the digital-only "neobank" owned by BBVA Compass, is testing out its second product, a contemporary twist on the traditional joint account.

Called Simple Shared, the no-fee product is intended to help the company's young, smartphone-toting customer base adapt as their lives become more complicated. It features transaction alerts and itemization of which accountholder paid for what. Rather than just for married couples, it is being marketed as a tool for a broad range of relationships involving financial transactions, such as roommates or parents and children.

"We don't ask because we don't care," said Derek Zumsteg, a product manager at Simple.

To get the joint account, a customer must already have a regular Simple account held at BBVA Compass, which acquired the fintech startup in 2014. (Those whose Simple accounts are held at its old partner bank, The Bancorp Bank, can ask to have the transfer of their funds expedited.) The joint account has a separate payment card but is managed with same mobile app as the basic account.

"We've spent years researching the intricacies of banking, account sharing, and most importantly, relationships and what people want from a Shared account," Josh Reich, co-founder and CEO of Simple, wrote in a draft blog post shared with American Banker.

"We're excited to get this out into the hands of more people and to continue rolling out new features that expand on our goal of building banking that can help people improve their relationships."

Simple claims it is "on track to be the fastest growing bank in the U.S.," with a 43% expansion of the customer base in the last six months.

The company has made small changes over the past year to please customers, such as eliminating a host of fees and launching a program that rewards word-of-mouth referrals with literal, physical wallets (in leather or felt).

The need for digital tools for couples has been expressed for years by industry insiders. Some personal financial management tools have functionality that lets couples communicate about transactions. Yodlee, the account aggregator owned by Envestnet, sells technology to banks that is designed to make banking simpler for people in relationships, for instance. And more recently, there have been tech efforts aimed at helping adult children manage their parents' money. But by and large, the digital options for couples and other relationships are few and far between.

For now, Simple's new product is in beta, so not everyone can immediately open an account. Amy Dunn, a spokeswoman for Simple, says some individuals will be prioritized based on how long they have been a customer or what Simple needs to test for (i.e. maybe the tech company needs more Android users).

In theory, two or more people could accomplish the same things using a traditional account or by reimbursing one another with tools like Venmo. But as Zumsteg sees it, the desire for a joint account – which many Simple users have requested – suggests they want an account that reflects the way they feel about the relationships.

"This is about an emotional bond and how people view it," Zumsteg said.