How to Error Proof a DCF Model
The DCF model states that the value of a company is equal to the sum of all of a company’s projected free cash flows (FCFs), which are discounted to the present date using an appropriate discount rate.
However, the discretionary assumptions used to project a company’s future performance are its main drawback, as these decisions are subjective and prone to the biases of the individual performing the analysis.
For that reason, the valuations derived from a DCF can vary greatly from each other.
The checklist below summarizes a few common errors often found in DCF models:
- Inclusion of Free Cash Flows (FCF) Before Year 1
- Too Short Initial Stage 1 Forecast Horizon
- Depreciation ≠ Capital Expenditures in Final Year of Forecast Period
- Mismatch in Free Cash Flows (FCFs) and Discount Rate
- Unrealistic Reinvestment Assumptions
- Forgetting to Discount Terminal Value (TV)
- Mismatch in Exit Multiple and Valuation Multiple
- Terminal Value > 75% of Implied Valuation
- Disregard of Relative Valuation — No “Sanity Check”
Mistake 1. Inclusion of Free Cash Flows (FCF) Before Year 1
The first mistake seen in DCF models is accidentally including the latest historical period as part of the Stage 1 cash flows.
The initial forecast period should consist of only projected free cash flows (FCFs) and never any historical cash flows.
The DCF is based on projected cash flows, not historical cash flows. While most understand this concept, many DCF models are linked from a separate tab, where the historical periods will also be carried over and may be erroneously linked into the DCF calculation.
As a result, make sure to discount and add only the company's future cash flows.
Mistake 2. Too Short Initial Forecast Horizon (Stage 1)
The next error is related to having an initial forecast period that is too short, i.e. Stage 1.
For a mature company, a standard five-year forecast horizon is sufficient, i.e. the company is established with predictable cash flows and profit margins.
The time necessary for a mature company to reach a long-term sustainable state is brief — in fact, it could be even shorter than five years, if appropriate.
On the other hand, certain DCF models performed on high-growth companies need to extend the initial forecast period to a ten or even fifteen-year horizon.
Ask yourself, “Can this company continue to grow at this growth rate perpetually?”
If not, the forecast should be extended until the company matures further.
However, note that the longer the initial forecast period, the less credible the implied valuation is — which is also why the DCF is most reliable for mature companies with established market positions.
Mistake 3. Depreciation % of Capital Expenditures Converge into Final Forecast Period
Closely related to the prior mistake, a company’s depreciation as a percentage of its capital expenditures (Capex) should converge near a ratio of 1.0x, or 100%, by the end of the initial forecast period.
As a company matures, the opportunities for capital expenditures decline, resulting in less capex overall. More specifically, the majority of the company’s capex will be maintenance capex, as opposed to growth capex.
Given the reduced capex, having depreciation outpacing capex perpetually would be unrealistic as depreciation cannot reduce the value of a fixed asset (PP&E) below zero.
Mistake 4. Mismatch in Free Cash Flow (FCF) and Discount Rate
The most common DCF model is the unlevered DCF, where the free cash flow to firm (FCFF) is projected.
Since FCFF represents the cash flows that belong to all stakeholders, such as debt lenders and equity holders, the weighted average cost of capital (WACC) is the appropriate discount rate to use.
In contrast, the levered DCF — which is used far less common in practice — projects the free cash flow to equity (FCFE) of a company, which belongs solely to common shareholders. In this case, the correct discount rate to use is the cost of equity.
Mistake 5. Unrealistic Reinvestment (Capex and Change in NWC)
Generating future growth requires spending, so it cannot just be reduced without reason.
Of course, reinvestments such as Capex and the change in net working capital (NWC) will gradually decrease as a company matures and revenue growth slows down.
Yet, the reinvestment rate must still be reasonable and in line with that of the company’s industry peers.
For example, a company can be assumed to grow at 2.5% perpetually, but rational assumptions must be made where the continued revenue growth is supported, as opposed to simply cutting reinvestments to zero.
Mistake 6. Forgetting to Discount Terminal Value (TV)
After calculating the terminal value (TV), a crucial next step is to discount the terminal value to the present date.
An easy mistake to make is to neglect this step and add the undiscounted terminal value to the discounted sum of the free cash flows (FCFs).
The terminal value is calculated using either:
- Perpetuity Growth Method (or)
- Exit Multiple Methods
But regardless of which approach is used, the terminal value calculated represents the present value (PV) of the company’s cash flows in the final year of the explicit forecast period prior to entering the long-term perpetuity stage, not the value as of the present date.
Since the DCF estimates what a company is worth as of today, it is necessary to discount the terminal value (i.e. the future value) to the present date, i.e. Year 0.
The following formula is used to discount the terminal value.
Present Value of Terminal Value Formula
- Present Value of Terminal Value = Unadjusted TV / (1 + Discount Rate) ^ Years
Mistake 7. Unrealistic Terminal Growth Rate Assumption
The terminal growth rate assumption refers to the growth rate at which a company is expected to grow at into perpetuity.
One common error seen — particularly for high-growth companies — is an unrealistic terminal growth rate, such as 5%.
If a company is growing quickly far above its peers, extend the explicit forecast period until its growth rate normalizes.
A reasonable terminal growth rate assumption should generally be in line with the GDP growth rate, i.e. between 2% to 4%.
For a long-term growth rate in the upper part of that range (i.e. 4%), there should also be a valid reason supporting that assumption — e.g. a market leader such as Amazon (AMZN).
Otherwise, the terminal growth rate of most companies should be around 2% to 3%.
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