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How to Update Your Model Mid-Fundraise Without Losing Consistency



Author: Yanni Papoutsi - Fractional VP of Finance and Strategy for early-stage startups - Author, Raise Ready Reading time: ~10 min

Why Models Change Mid-Fundraise

A fundraising process for a seed or Series A round typically runs 12 to 20 weeks from first meetings to close. Over that period, three types of changes happen to a financial model. The first is investor-driven. A VC challenges a specific assumption in a meeting and the founder agrees the challenge is valid. The CAC assumption was too optimistic given what the founder has learned from early customer acquisition. The gross margin does not fully account for customer success costs. The revenue ramp in year two assumed a sales hire who now will not be in place until month 14 rather than month 10. The second is data-driven. New monthly actuals come in. A month that was forecast in the model can now be replaced with real numbers. Sometimes the actuals are better than plan. Often they reveal gaps in the model's assumptions. Either way, the model should be updated. The third is strategic. The pricing model changes. A new enterprise tier is added. The go-to-market motion shifts from inbound to outbound. A key partnership materializes that changes the customer acquisition model. All three types of changes are legitimate. The problem is execution: how do you make these updates without inadvertently creating a model where different tabs reflect different versions of the truth?

The Architecture That Makes Consistent Updates Safe

The single most important structural choice in any financial model is centralized assumptions. Every material input lives in exactly one cell in the assumptions tab. Every formula in the model that uses that input references that cell. When the assumption changes, changing the single source cell flows the update through the entire model automatically. This sounds obvious. It is surprisingly rare in practice.

The most common alternative is a model where key assumptions are repeated in multiple tabs. CAC appears in the revenue model tab, the marketing spend tab, and the board summary tab. Each time someone updates the model, they might update one or two instances and miss the third. The model then contains three different values for the same assumption, none of which are labelled as the current version. If your model is built this way, the fix before sending to investors is to consolidate every material assumption into the assumptions tab, build a reference from every formula that uses it, and verify the update flows correctly by changing a value and checking all downstream effects. The categories of assumptions that most commonly need consolidating: Revenue assumptions: average contract value, conversion rates at each funnel stage, churn rate, expansion revenue percentage. These often appear separately in the revenue model, the LTV calculation, and the summary metrics tab. Cost assumptions: salary bands by role, employer overhead percentages, headcount productivity ramp timelines. These often appear in a headcount tab but are disconnected from the scenario model. Timing assumptions: first revenue month, first sales hire start date, product launch date. These are frequently hardcoded in different cells across multiple tabs rather than referenced from a single source.

Version Control: The Practice That Prevents Disaster

Every time a material update is made to the model, save a new version with a consistent naming convention. The format that works: CompanyName_Model_v[number]_[YYYYMMDD].xlsx Example: Simplifii_Model_v4_20250308.xlsx

This naming convention creates a complete audit trail of every version sent to every investor. When an investor references a number in a follow-up email three weeks after your last meeting, you can identify exactly which version they are working from and compare it to the current version. What not to do: overwrite the previous version without saving a copy first. Use naming conventions like "final," "final_v2," "FINAL_REAL," "latest." These are all jokes that become nightmares during diligence. What to do: create a folder structure that makes version management automatic. A folder called "Model Versions" with every version saved chronologically. A separate folder called "Investor Versions" with the specific version sent to each investor, named by investor name and date. When sending an updated model, specify exactly what changed. Not "updated model attached." Something like: "Updated model attached, version 5 dated 8 March 2025. Changes from v4: CAC assumption updated from GBP 320 to GBP 380 reflecting February actuals. This moves base case 18-month runway from 14 months to 12 months. Conservative scenario runway moves from 10 months to 9 months. No other material changes." This communication practice does two things. First, it respects the investor's time by telling them exactly what to look at. Second, it creates a written record of every model update, which is valuable if there are any questions during diligence about when assumptions changed and why.

Handling Different Versions with Different Investors

One of the more delicate situations in a fundraise is managing investors who received different versions of the model. An investor who received version 2 in January may have built their own analysis on those numbers. If version 5 in March has materially different assumptions, that investor needs to know. The rule: any investor in active conversation who received a previous version should receive the updated version with a clear change summary. Do not assume they will ask. Do not wait until the next meeting. Send it proactively with an explanation. If an assumption change makes the business look materially worse (a revenue forecast cut, a runway compression, a gross margin reduction), the proactive update is particularly important. Investors who discover that numbers have changed without being told directly will interpret the lack of communication as concealment. The damage from that interpretation is far greater than the damage from the underlying assumption change. The one exception: if an investor has already passed on the deal, there is no obligation to send updates. But if they are still engaged, tracking the company, or have expressed interest in re-engaging at the next milestone, keep them on the update list.

The Three Most Destructive Mid-Raise Update Mistakes

Updating the model without updating the assumptions tab.

This happens more often than any other consistency error. The founder changes a number in the revenue model tab because an investor challenged the assumption. But the assumptions tab still shows the old value. An investor who opens the model and compares the assumptions tab to the revenue model will find the discrepancy immediately. The model looks inconsistent, and the assumption cannot be defended because it is not documented. Sending an update without explaining what changed.

An investor who received the previous version needs to know what is different. Sending version 5 without noting that it is version 5, without explaining what changed from version 4, forces the investor to compare documents line by line. Most will not do this. They will either use the old version or ask you to summarize the changes, which means an additional email exchange that could have been avoided. Changing assumptions in one tab but not in dependent tabs. A pricing change that flows through the revenue model but not through the LTV calculation. A headcount timing change that affects the cost model but not the productivity ramp assumptions in the revenue model. A churn rate change that updates the revenue forecast but not the cohort retention chart used in the investor summary. The fix is systematic: after every material update, open every tab and ask whether this change has any implication for the numbers here. Do not rely on memory. Do not assume the formulas are connected. Check each one.

Knowing When to Hold and When to Update

Not every investor challenge should result in a model update. Part of fundraising is defending your assumptions when you believe they are right. If an investor challenges your CAC assumption and you have 90 days of actual data supporting it, the right response is to defend the assumption, not to change it. The distinction is between a legitimate new input that changes your view, and an investor preference for more conservative assumptions. The former warrants updating the model. The latter warrants a conversation about why your assumptions are defensible. If you do change an assumption in response to investor feedback, the change note should reflect honest reasoning: "updated based on actual data now available" or "updated based on a revised view of the enterprise sales cycle following conversations with prospects." It should not say "revised based on investor feedback" unless the feedback contained new information you did not previously have.

When an Update Should Trigger a Conversation, Not Just a File

Some model updates are administrative. You updated last month's actuals, nothing material changed, here is the current version. Send it with a brief note and move on. Other updates cross a threshold where the model update alone is insufficient. These are the moments when the change is significant enough that an investor deserves a call before they see the revised file. The situations that warrant a proactive call rather than just an updated model: A key assumption is being changed because the business performed materially differently than planned, not because of new data or new thinking. If revenue in the most recent month was 30% below plan, that is a conversation, not just a spreadsheet update. A scenario that was previously described as the base case is now looking like the optimistic case. If the conservative scenario has become the base case, investors need to hear that framing before they see the numbers. Runway falls below a threshold that changes what is possible. If the model update reveals that runway at current burn is now under nine months rather than fourteen months, that changes the context for every other conversation in the fundraise. The principle is: investors should never receive a materially worse model without also receiving a conversation that provides context. The context does not change the numbers. But it gives the founder the opportunity to explain what they have learned, what they are doing about it, and why the thesis is still intact. Receiving a worse model without context leaves the investor to draw their own conclusions. Those conclusions are rarely as optimistic as the founder's.

FAQ

How often should the model be updated during an active fundraise? Material changes should be reflected as soon as possible. Minor updates (new monthly actuals with no material variance from plan) can be batched into a monthly update. Do not send multiple versions per week unless there is a genuinely significant change each time. Frequent small updates create noise and suggest the model is not stable. What if different investors are at different stages and have received different versions? Track it. A simple spreadsheet with investor name, version received, and date sent is all you need. When a material update is issued, every investor in active conversation gets the new version simultaneously with the same change summary. No investor should feel they received information later than another. Should the model include a "last updated" cell that is visible on the summary tab? Yes. Put the version number and last updated date on the summary tab. This removes any ambiguity about which version an investor is looking at and signals that the model is actively maintained.