The Mid-Year Convention in a DCF

Valuation · Updated June 2026

The mid-year convention assumes a company's cash flows arrive evenly through the year rather than all on the final day. Instead of discounting year one at a full period, you discount it at half a period, then year two at one and a half, and so on. Because the cash arrives sooner on average, the present value is slightly higher than under year end discounting.

Why use half period discounting

Standard year end discounting uses 1/(1+WACC)^t, which assumes all of a year's cash lands on the last day. In reality cash flows in throughout the year, so treating it as arriving at the midpoint is more accurate.

The mid-year convention replaces the period t with t - 0.5, giving a discount factor of 1/(1+WACC)^(t-0.5). Year one is discounted at 0.5 periods, year two at 1.5, and so on. Each cash flow is closer to today, so its present value rises.

Worked example

Assume a WACC of 10 percent and year one free cash flow of 100. Compare the year end factor with the mid-year factor.

Year end factor for period 1: =1/(1.10)^1 returns 0.909.
Mid-year factor for period 1: =1/(1.10)^0.5 returns 0.953.
Present value of 100 at year end: =100*0.909 returns 90.9.
Present value of 100 at mid-year: =100*0.953 returns 95.3.
Build a toggle: =IF($B$1,C5-0.5,C5) for the exponent, where $B$1 is a 1 or 0 switch and C5 is the period.

Period	Year end exp	Mid-year exp	Factor diff
1	1.0	0.5	+4.8%
2	2.0	1.5	+4.8%
3	3.0	2.5	+4.8%

Each factor is larger by roughly (1.10)^0.5, about 4.9 percent, so every cash flow gains the same proportional uplift.

Toggling it cleanly in Excel

Make the convention a single switch so you can show both versions without rebuilding the model.

Put a 1 or 0 flag in a labeled input cell to turn the convention on or off.
Compute the adjusted period once, =Period - 0.5*Flag, and reference it in every discount factor.
Apply the same half period shift to the terminal value's discount factor for consistency.
Document the choice on the assumptions tab so a reviewer knows which convention drives the value.
Trace the discount factor cells to confirm the toggle flows through to every year and the terminal value.

Pitfalls

The most common error is applying the convention to the explicit cash flows but forgetting the terminal value. The terminal value sits at the end of the forecast and should be discounted on the same basis, otherwise the two halves of the DCF are inconsistent.

A second issue is double counting. If your Gordon growth terminal value already assumes mid-year cash flows, do not also apply the half period shift to it. Decide once where the convention lives and trace the factors to be sure it is applied exactly once.

Do it in one click

Formula Trace

Formula Trace follows your discount factor cells so you can confirm the mid-year toggle flows through every period and the terminal value exactly once.

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FAQ

Does the mid-year convention always increase value?

Yes, for positive cash flows. Shifting each flow half a period closer to today reduces the discounting, so the present value rises. The uplift is roughly one half period of the discount rate, often a few percent at typical WACCs.

Do I apply mid-year discounting to the terminal value?

Discount the terminal value on the same basis as the explicit flows so the model is internally consistent. The exact treatment depends on whether your terminal value formula already embeds mid-year timing, so apply the half period shift only once.

When should I not use the mid-year convention?

If cash flows genuinely arrive at year end, such as a single annual payment, year end discounting is more accurate. The convention assumes roughly even cash generation through the year, which fits most operating businesses but not lumpy schedules.