Cost ledger

In plain words

A cost ledger is a list of costs in which every entry carries the date it takes effect. When a cost changes, you add a new entry with its own date. The old entry stays.

This is what lets one report cover a year in which costs moved. An order from February is costed with February's unit cost and an order from March with March's. A single cost field per product can't do that: change it, and every past order is silently repriced.

Formula

• Cost of an order = for each cost, the entry with the latest effective date on or before the order's date

Worked example

The coffee bag's unit cost is $12.00 from 1 January and $13.50 from 1 March. Both entries are in the ledger.

For an order placed on 10 February the engine picks the January entry, and the order keeps $15.36. For one placed on 15 March it picks the March entry, and the same $40.00 bag keeps $13.86.

Computed by the margin engine in Offer Suite's own code, in whole cents, from a $40.00 bag of coffee with a $12.00 unit cost.

A ledger is not a price list

A price list holds the current cost of each product. It answers what something costs today and has no memory. A ledger answers what something cost on any date, which is the question every report about past orders is really asking.

Using it

Enter a cost with its effective date as soon as you know it, including dates in the future for a supplier increase you have been told about. Never fix a wrong cost by typing over it. Add the correction, with the date it should have applied from, and let the affected orders be restated.

In Offer Suite

Offer Suite keeps costs as a ledger. Every cost row has the date it applies from, and rows are appended and never edited. The ledger also records when each row was written, so it can answer both what an order cost and what was known when the order arrived.

Source: Offer Suite's cost ledger.