SumIt software grows 10x with BILL as AP partner

Family offices offer bespoke services to the wealthiest people in the world. White-glove tax planning. Mission-driven nonprofits built from scratch. But for many of these offices, the tech stack rests on off-the-shelf software built for the masses. SumIt set out to change that.

"We saw a deep need in the industry," says Alexandre Lin, CEO and Co-Founder, SumIt. "There was no good dedicated GL for the family office space. So we built one."

Lin partnered with a NASA aerospace engineer to craft the most intuitive GL solution for family offices, but when it came to bill pay, they didn't build. They partnered.

"You're never going to rebuild what BILL built," Lin says. "We're the best in the GL. We partner with the best in bill pay."

Challenge: Enterprise security, white-glove convenience

Family offices run on two non-negotiables. The software has to keep billion-dollar portfolios secure. And it has to feel effortless to the CFOs and family members who use it every day.

But the operational complexity is real. A single client's net worth can span hundreds of entities across dozens of jurisdictions, and wires can move in the millions. Approvals and audit trails have to be air-tight.

"Family offices deal with one entity paying a bill on behalf of five others," Lin says. "On a horizontal GL, that's hours of manual work, often in Excel. It's a specific pain point, and it shows up in every single client we talk to."

The clients themselves raise the bar. "Our clients are $100M-plus in assets and also multi-family offices who run the books for dozens of families," Lin says. "Quite a few of them are billionaires. You can't run that on software that wasn't built for the complexity, the privacy, or the precision the space demands."

Solution: One SumIt GL, multiple BILL accounts

Family offices run unique workflows. Wires clearing across multiple banks. Dozens of entities closing on the same calendar. SumIt built its software around those realities.

"Our integration with BILL is super simple," Lin says. "It feels familiar to anyone coming from a standard GL, but it's multi-entity. Multiple and inter-entity BILL accounts connected to one SumIt account, because that's what family offices actually need. You can pay your bill and split it across five entities with the right inter-entity journal entries, automatically created."

For principals who need to approve large wires and payments, BILL's mobile app handles those approvals with ease while preserving the security of over $100M portfolio demands. No spreadsheets. No printed approval logs. Just a phone, a fingerprint, and a digital paper trail that holds up to audit.

The result is a fintech stack with two top-shelf solutions, purpose-built for the industry's leading family offices.

Pilot: Bulletproof Capital

SumIt's first partner wasn't a focus group. It was a CFO with a 9-figure single-family office and strong opinions about what a modern GL should do.

Latesia Smoot, CFO of Bulletproof Capital says, "We run a very lean office, so time matters. I was looking for a solution that understood how family offices actually work: multiple entities, inter-entity activity, and a lot of detail that needs to be right. I wanted something that would reduce manual input, give us better visibility across entities, and help the accounting stay current without adding more process. With SumIt and BILL, we were able to save time and get closer to real-time insight into what was happening across the office.”

As one of the first pilot clients for the SumIt and BILL integration, Smoot helped shape dozens of early decisions.

“The biggest benefit for us was how much manual work it took out of the day-to-day. Instead of spending time re-entering information, tracking inter-entity activity separately, or waiting until later to understand where things stood, we had a cleaner workflow and more timely insight,” says Smoot. “For a lean office like ours, that makes a real difference.”

Bulletproof's pilot experience is the model for every client that came after.

"Bulletproof has seen this integration evolve from day one," Lin says. "That kind of partnership is what makes a specialized product actually work for the space."

The results: 10x growth, over 80 clients, zero shortcuts

The restraint paid off. In the two years since SumIt launched the product with BILL as its bill pay partner, the business has grown 10x. The team has scaled from four to 11. The platform now serves close to 50 wealth management firms and the over 80 families they look after.*

10x growth, one vertical. Every hire, feature, and integration point has been focused exclusively on the US wealth management market. No horizontal expansion. No side-quests into adjacent industries.

From four to 11, without compromising the bar. SumIt's engineering bar started with a NASA aerospace engineer and hasn't moved since. As an aerospace engineer, you need to be accurate with your numbers for obvious reasons. The rest of the team was built to match.

Trust as a growth strategy. In this tight-knit vertical, word travels. SumIt's growth has come largely from clients telling other family offices what's finally possible.

"We're known in the space for not over-promising," Lin says. "We do what we say we'll do. That matters in wealth management, where trust is everything. And we don’t try to do everything. We want to be the best at family office accounting. Period."

Looking ahead: A vertical that finally has its stack

SumIt's team is built around the same principle that shaped the BILL partnership: impeccable customer service with a clear focus.

"People love working with us because they love the people on the team," Lin says. "We care about their success. We take their feedback. We evolve the product as a result." In fact, in 2026, SumIt was awarded Best Family Office Accounting Software by the Family Wealth Report Awards. 

For the wealthiest families, white-glove service finally has software to match. And the builds are only accelerating.

"The software world is changing a ton," Lin says. "SumIt and BILL are making the right investments to stay ahead of the game."

^{*Results as reported by SumIt based on internal analysis of AP workflows across clients using the BILL API Platform April 2026. Results are based on the experience of a specific customer and are not a guarantee of future performance. Actual results will vary.}