- Model version
- 1.0
The formula, in words
- Money paid later is worth less than money paid today, by the rate at which money costs you. Discounting each leg back to day zero and adding them up gives what the whole structure is worth as a share of the invoice.
- Annual compounding is used rather than simple interest, because the rate on the slider is an annual rate and legs often run beyond a year. (1+r)−d/365 is the same convention a treasury team would use, where r is the annual rate and d the payment day.
- An LC you pay for is a cost at day zero, so its full percentage comes straight off what the terms were worth. An LC the supplier pays for is their cost, and it appears in their column, not yours.
- The result reads two ways from one number, and that is the point. If your structure is worth 97.9%, the terms are worth 2.1% to you and cost the supplier 2.1%. A supplier asking 3% to change them is asking for more than the change is worth.
- The rate check prices the same two schedules at three annual rates, spaced three points apart and kept within the slider range. At each rate, the equal price on their offer is PVB100PVA, where PVA is the present value of your schedule and PVB that of their schedule, in percentage points.
- The peak carry is the largest absolute difference between the two cumulative paid percentages immediately after a payment date. Its window ends at the next payment date, when that difference can change.
- The weighted payment day multiplies each payment day by its share of the invoice. Stock days and customer credit days extend the cash cycle, while the weighted payment day shortens it.
- Prepayment discounts the face amount from maturity back to today, then removes the entered fees. The annualised figure scales that cost by the entered maturity.
where PV is the present value in percentage points, i indexes payments, pi the payment share in percentage points, and di its day. where V is the value of the terms to you in percentage points. The cost to the supplier is the same figure, from the other side.
The LC you pay for is added straight back onto what you effectively pay.
where P is the price with terms and P0 the invoice price. where PB is the equal price for offer B. where A(d) is the cumulative share paid by the specified day. where ΔP is the price move and r′ the rate checked. where Cmax is peak cash carry, AB(di) the cumulative share paid by B, and AA(di) that paid by A at each payment date. where dw is the weighted payable day. where dc is the cash cycle, ds stock days, and db customer credit days. where f is the discount factor, q the discount rate, and dm maturity days. where N is net proceeds, F the face amount, and C fees. where ra is the annualised cost and Ct the total cost. A worked example
30% on order, 40% on day 60, 30% on day 150, at 12% a year. The first leg is paid today, so it is worth its full 30%. The second is discounted by 1.12−60/365=0.9815, so 40% becomes 39.26%. The third is discounted by 1.12−150/365=0.9545, so 30% becomes 28.63%. Adding them gives 97.90%. The terms are worth 2.10% of the price, which is the number to put on the table when the supplier asks for cash up front, and the number to compare against whatever discount they offer for it.
Their default structure is worth 100.00%, so an equal invoice price is 100×97.8966÷100=97.8966. That is a 2.10% lower price. At week 8, which is day 56, your offer has paid 30% while theirs has paid 100%. The supplier is carrying the 70 point difference under your schedule at that week.
With the schedules held still, the gap is 1.61 points at 9%, 2.10 points at 12%, and 2.58 points at 15%. Their equal-value invoice is therefore 1.61%, 2.10%, or 2.58% lower at those rates. Across the nominal schedule, the largest cumulative payment gap is 70 points from day 0 until day 60: 100% has been paid under their offer and 30% under yours.
What this does not model
Currency movement between the legs, counterparty risk (which is usually the actual reason a structure exists), the credit line the LC consumes, bank charges beyond the single percentage entered, confirmation and discrepancy fees, the difference between a sight LC and a usance LC, tax timing, and any covenant that makes a payment date less flexible than a slider suggests. Discounting a schedule tells you what a structure is worth on paper. It says nothing about whether the counterparty will be there in 150 days, and that judgement is not arithmetic.
The cash cycle treats the entered stock days, customer credit days and weighted payment day as fixed. It does not model changes in demand, customer payment behaviour or bank availability. The prepayment arithmetic prices only the entered face, maturity, rate and all in fees, and does not say that a bank will make the advance.
Where this comes from
The prepayment structure is described from UCP 600 and from the ICC's practitioner collection on it, ICC Publication 682. Both are named and neither is reproduced: no article text, no definition and no time limit is quoted here, and where a credit or a bank's own undertaking says something different, that governs and not this page.