Capital Allocation Model | NPV, IRR & Project Ranking

Every pound a business spends is simultaneously a decision not to spend it on something else. A mid-market manufacturer with £5 million earmarked for capital investment can build a new production line, upgrade its warehouse, replace its ageing fleet, implement an ERP system, or launch into a new market — but rarely all of them at once. The job of the finance team is not simply to say whether each project is financially viable in isolation. It is to figure out which combination of projects creates the most value within the constraint of the available budget.

This is capital allocation: one of the most consequential decisions a corporate finance team influences, and one of the areas most frequently examined in finance interviews. Most students encounter NPV and IRR as abstract formulas. This post puts them to work in a real multi-project allocation decision for CapitalCo, a mid-market UK manufacturer with eight competing investment proposals and a £5 million budget.

The Three Standard Appraisal Metrics

Before you can rank projects, you need to be fluent in the three metrics that drive every capital budgeting decision.

Net Present Value (NPV)

NPV is the theoretically correct measure of value creation. It calculates the sum of all discounted future cash flows from a project and subtracts the initial investment.

NPV = −Investment + Σ [CFt / (1 + r)^t]

Where r is the discount rate — typically the company’s WACC or a project-specific hurdle rate — and t is the year. The decision rule is simple: invest if NPV > 0, because the project returns more than the cost of capital. When ranking competing projects, choose the higher NPV.

The reason NPV is preferred is that it measures value in absolute pound terms. A project with an NPV of £500k creates £500k of wealth for shareholders. That clarity is hard to argue with.

Internal Rate of Return (IRR)

IRR is the discount rate at which the NPV of a project equals zero — the break-even rate of return. The decision rule: invest if IRR exceeds the hurdle rate.

0 = −Investment + Σ [CFt / (1 + IRR)^t]

IRR is popular in practice because it communicates returns as a percentage. Telling a board that a project “returns 21% on our capital” is more intuitive than saying it has an NPV of £340k. But IRR has a critical flaw: it implicitly assumes that all interim cash flows can be reinvested at the IRR itself. For a high-returning project, this assumption is almost always unrealistic.

The fix is Modified IRR (MIRR), which explicitly separates the finance rate (cost of funding) from the reinvestment rate (where interim cash flows are reinvested). MIRR almost always gives a more conservative — and more credible — return figure.

MIRR = (FV of positive cash flows / PV of negative cash flows)^(1/n) − 1

In Excel: =MIRR(cash_flows, finance_rate, reinvestment_rate)

Payback Period

Payback measures how quickly the initial investment is recovered from cumulative cash flows. It is simple, intuitive, and widely used — especially by capital-constrained businesses that care about cash timing as much as total value.

Its limitation is that it ignores the time value of money and disregards all cash flows beyond the payback date. A project that pays back in year 3 but generates most of its value in years 4 through 8 looks identical — by payback alone — to one that pays back in year 3 and then flatlines. Use Discounted Payback (applying the discount factor before accumulating) to correct for the time value problem.

Quick comparison for a single project (£500k investment, £150k/year for 5 years, WACC 10%):

Metric	Value	Interpretation
NPV	£68.6k	Positive — creates value
IRR	15.2%	Exceeds 10% hurdle
MIRR (at 10%)	12.8%	More conservative; more realistic
Payback	3.3 years	Recovered in year 3
Discounted Payback	4.1 years	Adjusted for time value

Building the Single-Project Appraisal

Let us walk through the full Excel build for CapitalCo’s first project: a new production line.

Project A — New Production Line

Initial investment: £1,200k at Year 0
Incremental revenue uplift: £400k per year
Incremental operating costs: £200k per year
Incremental FCF: £200k per year (Years 1–6)
Salvage value at Year 6: £100k
Discount rate: 12%

Year-by-year cash flow table (£k):

	Year 0	Year 1	Year 2	Year 3	Year 4	Year 5	Year 6
Investment	(1,200)	—	—	—	—	—	—
Operating FCF	—	200	200	200	200	200	200
Salvage value	—	—	—	—	—	—	100
Net cash flow	(1,200)	200	200	200	200	200	300
Cumulative	(1,200)	(1,000)	(800)	(600)	(400)	(200)	100

Excel formulas:

NPV  = =NPV(0.12, C3:H3) + B3
     → Result: £(22)k  [slightly negative at 12% — marginal project]

IRR  = =IRR(B3:H3)
     → Result: 11.5%  [below 12% hurdle — confirms marginal status]

MIRR = =MIRR(B3:H3, 0.12, 0.08)
     → Result: 10.1%

Payback = MATCH(0, SIGN(cumulative_row), 0) − 1 + ABS(last_negative / next_positive)
     → Result: 5.7 years

Note the consistency: NPV is negative, IRR is below the hurdle, and payback is almost the length of the project life. This is a marginal investment at a 12% hurdle rate. At 10%, the NPV turns positive (£68k). The sensitivity to the discount rate is an important discussion point with management.

Ranking Multiple Projects: The Capital Allocation Scorecard

CapitalCo has eight proposals. With a £5 million total budget, not all can be funded. Here is the full scorecard, ranked by NPV:

Project	Investment £k	NPV £k	IRR %	MIRR %	Payback (yrs)	Strategic fit (1–5)	Rank
New Production Line A	1,200	485	18.0	14.2	3.2	5	1
New Production Line B	1,000	320	16.0	13.1	3.8	4	2
ERP System	800	210	14.0	11.8	4.1	5	3
New Market Entry	900	175	13.5	11.2	4.4	4	4
Warehouse Upgrade	600	140	15.2	12.4	3.6	3	5
R&D Programme	500	95	12.8	10.9	4.9	5	6
Fleet Replacement	400	60	11.8	10.2	5.1	2	7
Sustainability Upgrade	300	(45)	8.5	7.8	6.2	4	8

With a £5m budget and projects ranked by NPV, the recommended portfolio is:

Fund in full: Projects 1–5 (total: £4,500k, combined NPV: £1,330k)
Partially fund: Project 6 — the R&D programme (£500k remaining budget fits exactly)
Defer: Projects 7–8

Total committed: £5,000k. Total NPV created: £1,425k.

Compare this to a purely IRR-ranked selection. IRR would push the Warehouse Upgrade (15.2% IRR) above the New Market Entry (13.5%) and deprioritise the ERP system — even though NPV shows the ERP creates more absolute value. IRR-ranked portfolios consistently underweight large, moderate-return projects in favour of smaller, high-return ones. The difference compounds across an entire capital cycle.

Adding a strategic overlay

Pure financial ranking can miss regulatory necessities and strategic imperatives. Note that the Sustainability Upgrade ranks last on NPV — it has a negative £45k NPV at the 12% hurdle. But if it is required to meet incoming environmental regulation, deferring it is not a real option. The cost of non-compliance (fines, reputational damage, loss of operating licence) is simply not captured in the NPV calculation.

The strategic fit score (1–5) in the scorecard forces this conversation into the open. A project scoring 4 or 5 on strategic fit with a negative NPV should trigger a management discussion about whether the hurdle rate is the right lens — not automatic rejection. In practice, the finance team’s job is to make the trade-off explicit, not to make the decision unilaterally.

Common Mistakes in Capital Allocation

Using IRR alone and ignoring scale. A £10k project returning 40% IRR creates £4k of value. A £5m project at 15% IRR creates £750k. Ranking by IRR alone would fund the former and reject the latter. NPV prevents this error because it measures value in absolute terms.

Forgetting incremental costs. Every cash flow in the appraisal should represent the change caused by the project, not the total business result. If a new production line requires dedicated management time that is currently unallocated, that management cost is incremental. If it uses existing spare capacity, it is not.

Optimistic bias. Project sponsors have strong incentives to overstate benefits and understate costs. Post-investment reviews consistently show that forecast NPVs exceed actual NPVs by 15–30% on average. Experienced finance teams apply a systematic haircut to sponsor projections — or use a higher hurdle rate for internally proposed projects than for market acquisitions.

Ignoring working capital. A new product line requires inventory ahead of the first sale and extends credit to new customers. These are real cash outflows that reduce the Year 1 and Year 2 FCF. New analysts frequently model revenue and operating costs but leave the working capital row blank. Do not.

How Capital Allocation Works in Practice

The annual capital budgeting cycle at most mid-market businesses follows a predictable rhythm. In Q3, business unit leaders submit project proposals. The finance team standardises the appraisal methodology — consistent discount rates, consistent treatment of working capital and depreciation — and compiles the consolidated scorecard. In Q4, the board reviews and approves the capital budget.

What happens next matters as much as what gets approved. Projects rarely unfold exactly as projected. A well-run finance function builds in a mid-year reallocation review: if a high-priority project completes early or comes in under budget, that freed capital should be redeployed — not simply returned to the centre to accumulate.

Finally, the post-investment review closes the loop. Three years after a project completes, the finance team should go back and ask: what IRR did we actually achieve? Where did the projection go wrong? The answers improve the next round of appraisals. It is also a powerful check on optimistic bias — project sponsors who know their forecasts will be audited tend to submit more credible ones.

Key Takeaways

NPV is the correct primary metric for capital allocation because it measures value creation in absolute £ terms — always lead with it
IRR is useful for communicating returns but must not be the sole decision criterion; it favours small, high-return projects over large, moderate-return ones
MIRR corrects IRR’s reinvestment-rate flaw and should be reported alongside IRR for any project where the two diverge materially
Always rank projects against the budget constraint, not in isolation — the goal is to maximise total NPV within the capital envelope
Qualitative factors (strategic fit, regulatory necessity) must be made explicit in the framework, not left to back-room conversations
Post-investment reviews are essential: they reduce optimistic bias and sharpen the quality of future appraisals

Practice

Build the CapitalCo scorecard for all eight projects using the cash flow assumptions above. Then apply a £4m budget constraint and identify the optimal portfolio using NPV-ranked selection. Compare the result to a purely IRR-ranked selection — note which projects differ between the two portfolios and calculate the NPV cost of ranking by IRR instead of NPV. As a final step, assume the Sustainability Upgrade becomes legally mandatory: how does this constraint change the optimal portfolio, and which project gets displaced?

Capital Allocation Model: How Companies Decide Where to Invest Their Money