Introduction
We all do it. We overlook the potential benefits of spreadsheet modeling by discarding the financial and operational models left behind when we join a new company. According to competitor analysis, forward-thinking finance teams leverage spreadsheet models and deeper spreadsheet modeling and decision analysis to unify data, reduce friction, and drive better outcomes. More often than not, we rename the previous models “legacy” and build new ones from scratch. There’s some logic behind it: the new leader usually has more experience, the last leader “did it differently,” and taking ownership of something you didn’t create feels uncomfortable. But DON’T!
I’ve been there. I came in, scrapped the operational model first, and then rebuilt everything, from CAC reports to Sales pipelines to SaaS metric waterfalls, to Cohort analyses. Sure, they required a few manual copy-pastes from our accounting system (a story for another time), but within a few months I had rebuilt every report.
The problem: it didn’t result in better business outcomes. It took months to get others on board. It was a huge time drain during a critical period for the company. And worst of all? I spent so much time creating models, that only our team knew how to update them.
When I left, the next finance leader restarted the cycle, introducing their own “improved models.” Department heads, executives, and employees were left dealing with a revolving set of tools that simply reintroduced the same numbers.
The real key is to build models that simplify the decision by letting teams learn them once and then focus on making the right decisions. Models that others trust and use long after you’re gone. You want them to be excited to use the tools, not stuck trying to understand them. You want them focused on understanding how the variables move, not what they are.
So, before you jump into changing every model, give yourself some time and scope to make a real difference and avoid a Sisyphean model rebuild process.
The Bullets:
Everyone loves to revamp models, and so did your predecessor. If you are going to rebuild a model, do it right to save the company time and confusion for years to come.
Wait three months before overhauling any model. Use that time to make small tweaks, observe how each team uses the numbers, and understand the existing workflow.
Focus on making your models intuitive, professional, and seamlessly integrated into your tool stack. The future will thank you.
The specifics:
1. Delay updating models for at least three months after your start
Yes, several of the current models being used are deeply flawed, and you want to bring immediate value to the company. So what could be better than updating them? Almost anything else. Models themselves don’t bring value, and model rebuilds, even less. By waiting several months, you’ll understand the context to guide meaningful improvements. The pause allows you to:
Understand the business. Yes, they are clichés, but “details matter” and “everything is connected.” Before you begin a pipeline report: How do campaigns generate SQLs? At what cost? Are those SQLs defined and evaluated in an objective way?
Fully grasp the assumptions. Why is only 50% of Customer Service cost allocated to R&D? Why are partnerships being checked against business development totals? Why are SDRs in sales and not marketing? There’s usually a method to the previous leader’s “madness.”
Update the models yourself. Follow the previous builder’s instructions. Yes, the first time will take longer. But as you work through it, you’ll gain insight into the process: the edge cases and how much time (or value) a full rebuild would actually save.
Establish your baseline metrics. Industry research shows the most effective CFOs understand the baseline so that they can set clear metrics for success going forward. It’s no use improving if you don’t understand what you are improving upon.
Eventually, you’ll need to update models when they fail to scale. But if you wait before diving in, you’ll be able to build something that adds lasting value, no matter the company’s size or direction.
Tip: In your first 90 days, focus on delivering real value. Increase cash collections. Generate risk-free returns from the treasury account. Analyze campaign-by-campaign pipeline results to improve marketing spending. Anything “real.” These actions will teach you far more about the company than a model revamp ever will.
2. Tweak previous solutions until you are ready to build a permanent one
There’s a reason builders get more excited about new houses than fixing up old ones. Just ask any builder. Knocking down walls? Fun. Dealing with 10-year-old plumbing. Not so much. But here’s the problem: key stakeholders are accustomed to the old model, even if they complain about it. So, try to eke out more mileage from your predecessor’s work. To do so:
Update summary tables with your formatting preferences. A simple refresh signals new ownership without unnecessary effort.
Add clear descriptions throughout. What confused you when you first opened the model? Sometimes, a well-placed label or short explanation is all that’s needed to greatly increase engagement.
Create new tabs only if absolutely necessary. Link numbers directly from existing tabs. Yes, best practice is building new reports using SUMIFS from data tables, but the goal here is efficiency, not a full redesign.
Link directly to actuals or other sources. If the model relies on manual copy-pasting, start creating data linkages to make reports live.
Sometimes a fresh coat of paint is all it takes. Leave the full model revamps for a time you're ready to build “the one” that will last.
Tip: Create a prioritization list as you extend the previous model's runway so that when you do make changes you start with the high-impact low-effort first.
3. Spend real time understanding how models help each team
Who is actually using these models? And how are they using them? This is the key to knowing which changes matter and which are just cosmetic. This process takes months, so don’t rush it:
Talk to department heads. How do they use models? When and where do they rely on them? Do they make decisions based on them, or are they just a formality?
Sit down with the CEO. Go through a couple upcoming decisions (pricing, expansion, feature development) and ask what data she looks at to make a decision.
Ask the accounting team what they look at. (Hint: Do they look at it at all?) Find out whether they trust the model, and more importantly, why or why not.
Watch how people use models in practice. People will often say they use a model, but their actual decision-making process tells a different story. Be in the room when key decisions are made.
Identify quick wins. Keep a list of small tweaks that can improve their decision making process. Make these tweaks (if possible) immediately to establish goodwill.
There’s no need for a formal “kick-off” process here. These conversations should happen informally and continuously as you get deeper into the business.
Tip: Ask people key information in other teams' models. For example, how does accounting look at and rationalize New ARR added in sales models? This will give you an insight into how cross-functionally teams think and any potential disconnects.
4. When you do a revamp… make it last
Alright, you know the business and have seen how a better model will improve each team’s decisions. Now, how do you ensure a model stands the test of time? While we cover model creation in-depth elsewhere, here is a quick checklist for "lastability:"
Tech stack integration. Models fail when they rely on manual copy-pasting from various systems, leaving them prone to error and reliant on specialists to get actuals.
Easy to update. Clearly marked inputs and outputs. Provide step-by-step update instructions and troubleshooting tips (e.g., “If this breaks, check X”) so teams can access their own numbers without always coming to you.
Always live. Teams should be able to check the numbers anytime, not just at month-end. If people have to ask whether it’s “up-to-date,” your model isn’t trustworthy.
Backward consistency. This model should hold up through multiple rounds of due diligence. Past results should remain consistent to avoid having five different spreadsheets that require explanations for minor discrepancies.
Scenarios. You’ll always hear questions like: “What if usage jumps 20%? How would that affect NDR?” Make it easy for teams to test these hypotheses so you can answer and move forward quickly.
The goal is to build a model that outlives you. One that future finance teams can build on seamlessly and that the organization actually trusts and uses.
Tip: All models should have a consistent structure to help other teams read them easily.
5. Enhance Your Spreadsheet Modeling Process
In theory, every team could run an HRIS, ERP, or CRM on spreadsheets. But modern businesses don’t because these systems provide structured operational value. So why should finance be different? At Abacum, we’ve seen this issue too many times, which is why we built our platform. But regardless of the tool you choose, use a tool that structures data across all leads and ensures a:
Centralized structure. Ensure you have one place that pulls in all parts of the business so you can stay within the system to review any numbers.
Continuation as the business evolves. Support complex business rules, scenario planning, and structural changes without requiring a full rebuild every time something shifts.
Simple navigation for non-finance teams. Encourage self-service by making insights accessible as finance shouldn’t be a black box.
Enforced controls and governance. Set clear data permissions and ensure consistency, error prevention, and version control, things spreadsheets fail at.
Unify all reporting in one system. Automate board reports, budgets, pipelines, and forecasts so you can focus on insights, not formatting and number-checking.
We’ll admit that we’re biased, but we’ve seen how constant model rebuilding over time undermines good decision-making more times than we can count.
Tip: A structured tool allows you to set up for any transition. There is a reason nobody goes back to spreadsheets.
In conclusion
You don’t want to get caught in the Sisyphean loop of finance constantly redoing models. It strains your team, erodes buy-in, and turns you into a single point of failure that will collapse when you leave. Instead, take the time to understand the business, be a 10x CFO, and build a robust system that engages the entire company.
This can be your legacy.
