What it means
Lease or buy is a capital budgeting question, and NAL answers it by pricing both paths in today's money and taking the difference, so the decision rests on arithmetic rather than habit. The buy side carries real costs and shields: ownership means the purchase price, maintenance and the lost lease deductions, offset by depreciation tax shields and whatever residual value the asset keeps.
The lease side is a stream of payments. Lease rentals are tax-deductible, the lessor claims the depreciation, and at the end the asset goes back unless a purchase option changes the story.
After-tax cash flows are the honest inputs, because depreciation shields, rental deductions and interest all move the comparison substantially. The discount rate does heavy lifting.
Standard practice discounts lease cash flows at the after-tax cost of debt, since lease obligations behave like debt, and academic treatments of lease analysis formalise exactly this approach. Sensitivity decides borderline cases, as residual value assumptions, tax rates and the discount rate can flip a small NAL, so thin margins mean the decision is genuinely uncertain rather than wrong.
The metric has famous detractors too, since some economists argue leasing only wins when lessor and lessee face different tax rates or residual expectations, which makes a positive NAL a clue to ask what the other side sees. For a business owner weighing a van fleet or machinery, NAL is the spreadsheet that ends the argument, because once both paths are priced honestly the decision stops being about the salesperson's monthly-payment framing.
Lease terms hide the economics, as maintenance bundles, mileage caps and early-exit clauses all carry present value, and a complete NAL prices every clause rather than the headline rental. The decision repeats at scale, since fleets, equipment schedules and property portfolios each generate the same question annually.
For finance teams the template is the asset: a disciplined NAL model, reviewed annually, converts every lease pitch into a comparable number, and the sales framing loses its power to confuse.
In practice
Real-world examples.
Example
A clinic leases diagnostic equipment after NAL analysis shows the technology's obsolescence risk outweighs ownership's residual value. Obsolescence risk tipped the scale.
Example
A manufacturer buys its lathes because taxable profits make the depreciation shields worth more than the lease's flexibility.
Example
A startup leases vehicles to conserve cash despite a negative NAL, treating the difference as the price of survival.
Formula
Calculation
NAL = cost of asset - present value of after-tax lease payments - present value of lost depreciation tax shields - present value of the residual value given up. All present values use the after-tax cost of debt. A positive NAL favours leasing; a negative NAL favours buying.
Worked example. A machine costs $100,000. The present value of the after-tax lease payments is $74,000, the present value of the depreciation shields lost by not owning is $15,000 and the present value of the residual value given up is $5,000. NAL = $100,000 - $74,000 - $15,000 - $5,000 = $6,000, so lease.
A sensitivity check shows how fragile the answer can be. If the residual value were worth $12,000 in present value instead of $5,000, NAL = $100,000 - $74,000 - $15,000 - $12,000 = -$1,000, and the answer flips to buy.Case study
Seen in the real world.
In this illustrative fictional case, Priya, finance lead at a logistics firm, evaluates leasing thirty delivery vans against buying. Her first model shows leasing ahead by $9,000 per van, but a sensitivity pass on residual values swings the answer by $14,000, which would turn the result into a $5,000 advantage for buying. She negotiates the residual assumption into a fixed purchase option, locks the favourable case, and presents the board a decision that survives its own assumptions. Across thirty vans the fixed option removes a swing of $420,000, so assumptions, not answers, needed negotiating.
Watch out
Common mistakes.
- Comparing monthly payments instead of present values, when timing, tax and residuals decide the true cost, and the monthly figure is marketing, not analysis. Present value is the only referee.
- Discounting at the cost of capital, when lease obligations are debt-like, and the after-tax cost of debt is the defensible rate in the standard method.
- Trusting a single-point NAL, when residuals and tax rates are estimates, and a decision that flips under small changes needs structure, not false precision.
Questions
People also ask.
What is net advantage to leasing?
The present value of leasing an asset minus the present value of owning it, both after tax. A positive NAL favours leasing; a negative one favours buying. The difference decides the path.
How is it calculated?
Price both paths in after-tax cash flows: lease rentals and lost depreciation shields against the purchase price and residual value. Discount at the after-tax cost of debt, the standard approach in academic lease analysis. Both sides are priced after tax.
When does leasing genuinely win?
When tax positions differ between lessor and lessee, when obsolescence risk is high, or when the lessor prices residual value more optimistically. A positive NAL asks what advantage the other side is monetising.
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