Engineering for Tax Season: How Column Tax Built the Most Reliable Infrastructure in the Tax Industry

At Column Tax, we’ve worked hard to build reliable infrastructure that performs when it matters most: tax season. This past season, we supported a seasonal surge of millions of users in our product without a single minute of downtime. Today we’ve sat down with Zach Ozer, Head of Infrastructure & Security, to understand the unique challenges of preparing for tax season and how Column Tax has earned its reputation as the most reliable infrastructure in the tax industry.

For taxpayers, early January often means the start of filing season. For Column Tax’s engineering team, it’s launch day. As Zach puts it:

“Most software products grow slowly. For us, everything happens all at once. Hardly anyone uses our product for months, and then starting in early January, suddenly millions of people show up at once.”

That seasonality shapes everything about how Column engineers, prepares, and scales its systems.

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Forecasting Traffic with Partners and Precision

Column works hand-in-hand with its partners, who notify the team about marketing pushes that will drive traffic.

“They’ll say, ‘We’re going to do a push campaign on January 5th, be prepared.’ And we’ll ask, ‘How many users are you sending this to? At what rate?’ These campaigns become some of the biggest drivers of our traffic.”

By coordinating with multiple partners, Column ensures campaigns don’t all overlap, shaping traffic in a predictable way.

Beyond partner collaboration, the team relies on increasingly sophisticated load testing. Every step of the tax filing journey — from filling out forms to sending returns to the IRS — is modeled in terms of compute time and database capacity.

“Now we actually know that each person’s tax return requires on the order of magnitude of one minute of processing time on our servers. We calculate that out and size the system accordingly — always keeping a 3x buffer on top of what our partners tell us.”

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Advancing Forward When Traffic Is Low

To meet each tax year’s unique challenges, Zach’s team has built a culture of preparation that leverages the seasonality of tax filing to their advantage.

“One principle we use a lot is ‘buy optionality.’ Any change we can safely make off-season, when traffic is low, is actually attractive — we might even stop the database for a while to restructure things. During peak season, we wouldn’t dare do this, but off-season, we can make those changes. That flexibility saves months of work later and ensures that during season, we have options to choose from.”

While other businesses must engineer cautiously year-round, Column’s off-season becomes a proving ground for forward-thinking infrastructure changes. This means that when millions of users arrive again in January, the system is prepared.

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Performance When It Matters Most

In the most recent tax season, Column’s infrastructure delivered a strong, resilient performance. As Zach put it:

That level of reliability is rare in any industry, and for enterprise partners, it means confidence that Column can deliver under the heaviest loads.

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How Infrastructure Weaves Through Everything at Column

For many people, “infrastructure” sounds like a back-office function. Zach is quick to dispel that idea.

For Zach, infrastructure isn’t just about servers or uptime metrics. It’s about trust. Every request matters because every request belongs to a person counting on Column to handle their taxes correctly.

“Tax calculations don’t have a lot of margin for error. In fact, there’s no margin for error. Your taxes are expected to be correctly calculated, and we guarantee that’s going to be true.”

And when things do go wrong, the stakes are high. Even small system errors can cause users to edit their tax data incorrectly, which Zach calls “potentially very bad for their return.”

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Lessons for Other Engineering Leaders

Not every company faces tax season, but many experience seasonal surges. Zach has advice for engineering leaders preparing for them:

• Know your seasons. Align your activities with them. Don’t try to do planning in the middle of peak — it won’t work.
• Treat different parts of the season differently. For us, we have two peaks: early filers and last-minute filers, with a lull in between. We plan code freezes around those phases, sometimes multiple freezes, so code keeps moving without creating risk.
• Load test aggressively. Estimate your users, test for that, then test for multiples of that. Build capacity accordingly.
• Stay flexible. For us, partners’ marketing pushes can change dates. If a push shifts from January 15th to January 17th, we change our scaling plan. It’s all about being adaptable and having options.
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Why It Matters

When companies choose to work with Column Tax, they’re not just choosing a reliable product with 100% uptime for their users. They’re choosing to work with a team that’s passionate about building systems that support millions of taxpayers with the same reliability as they would for just one.

While tax filing is a brief moment in time each year for most Americans, we prepare for it all year in advance to ensure every taxpayer has a great filing experience. The ingredient to success is by building a team that loves the unique challenges that come with the business. As Zach puts it:

“Unlike other companies who only face a launch surge once and then stabilize, we repeat this cycle every single year. It’s very exciting.”