Investment Appraisal for UK SMEs: NPV, Payback and the Cash Decision

Start with the decision and the alternative

Define what happens if you do nothing, then estimate only the cash flows that change because you invest. Compare realistic alternatives, including delaying the decision, repairing an existing asset or buying a smaller solution.

Historical spend that cannot be recovered is a sunk cost, not a new project outflow. Include installation, training, maintenance, incremental working capital and disposal cash where relevant. Discuss tax effects with your adviser rather than assuming the purchase price equals the after-tax cost.

A simple worked example

Assume an illustrative investment of £30,000 today produces net cash inflows of £12,000 at the end of each of the next three years, with no residual value, tax effects or further working-capital movements. Use a hypothetical 10% discount rate only to demonstrate the method, not as a recommended SME hurdle rate.

NPV is approximately £12,000 ÷ 1.10 + £12,000 ÷ 1.10² + £12,000 ÷ 1.10³ − £30,000, or negative £158. The proposal therefore falls slightly short of this assumed return requirement even though the undiscounted inflows total £36,000.

Payback answers a different question

If the example’s annual inflows arrive evenly through each year, simple payback is 2.5 years. If the money arrives only at year ends as assumed in the NPV example, cash is recovered at the end of year three; do not quietly mix those timing assumptions.

Simple payback ignores the time value of money and cash generated after recovery. A short-payback project can have less total value than a longer-lived alternative. Use it as a liquidity and exposure measure, not the sole decision rule.

Make the discount rate and risk explicit

A discount rate should reflect a justified required return and be consistent with whether the forecast is nominal or real and before or after tax. Using an unexplained rate from a template creates false precision. Seek advice where the decision is material.

Stress the assumptions that could actually fail: implementation delay, lower savings, weaker demand, higher maintenance or a shorter useful life. Avoid double-counting the same risk in both heavily reduced cash flows and an inflated discount rate without explaining the approach.

Check whether the business can fund the project

A positive NPV does not mean cash is available on the purchase date. Map deposits, staged payments, working-capital increases and financing terms onto the cash plan. Preserve enough liquidity for tax, payroll and operating commitments.

Separate the appraisal of the asset from the financing decision. Assess borrowing cost and restrictions, but do not insert loan proceeds as a project benefit while also ignoring repayment obligations. Keep the analysis consistent and understandable.

Approve assumptions and review the outcome

The decision paper should state the investment, alternatives, expected benefits, assumptions, NPV, payback, cash requirement and accountable owner. Include a date for checking actual performance against the case.

After implementation, distinguish missing benefits from delayed benefits and document what changed. The goal is not to defend a spreadsheet; it is to improve the quality of the next investment decision.

Sources and further guidance

• Scottish Government business guidance: investment appraisal
• Northern Ireland business guidance: investment risk and sensitivity

General guidance, not accounting, legal or tax advice. Confirm the treatment for your circumstances with a qualified adviser.