How Available-to-Promise Answers a Sales Question in EDGEBIC

Available-to-promise answers the question sales actually asks, which is not how much stock do we have but how much can I still sell without breaking a promise, and EDGEBIC answers it by reading the cumulative ATP column forward from physical on-hand. In EDGEBIC by User Solutions, available-to-promise (ATP) is computed as a running position across each supply event: how much supply lands, minus every firm order committed before the next supply lands. When a salesperson asks whether a new order fits, the cumulative ATP for that timeframe is the number that says yes or no safely.

This post shows how ATP turns a sales question into a defensible answer. For the underlying calculation, see available-to-promise in EDGEBIC; both live under the EDGEBIC planning guide.

Why on-hand is the wrong number to promise from

The instinct is to promise against on-hand. It is a trap. On-hand of 200 tells you nothing about whether 180 of those units are already spoken for by confirmed orders. Promise a new 100-unit order against that 200 and you have oversold by 80, with no warning until two customers want the same stock.

Available-to-promise fixes this by counting commitments. It starts from physical on-hand now, then subtracts firm demand as it walks forward, so what remains is genuinely free to sell. This is a different question from the projected available balance: PAB tells you what you will have, ATP tells you what you can still give away.

The two ATP figures per row

Each projection row carries two ATP numbers.

Discrete ATP appears at supply events: the current on-hand bucket, then every bucket where a build-to-stock order completes. Its value is the supply at that point minus all firm demand up to the next supply event. It can be negative when orders between two receipts outrun the supply.

Cumulative ATP carries the running total across supply events and holds steady between them. This is the number sales quotes: it is the total additional quantity you can promise through that point in time without breaking any existing commitment.

The split matters because a single supply event might be oversold (negative discrete) while the overall position is still healthy (positive cumulative), or the reverse. Reading both tells you not just whether you can promise, but where the tension is.

A worked sales question: 150 units by week 3

A customer asks for 150 units of a bracket in week 3. The bracket has 120 on hand. One build-to-stock order for 150 completes in week 2. Firm demand already on the books: 50 units due in week 1, 20 units due in week 2.

Walk the supply events forward.

Week 1 (on-hand supply point). Supply available = 120 on hand. Firm demand up to the next supply event (weeks 1 through 2) = 50. Discrete ATP = 120 − 50 = 70. Cumulative = 70.

Week 2 (receipt supply point). Supply = 150 (the completing order). Firm demand from week 2 forward = 20. Discrete ATP = 150 − 20 = 130. Cumulative = 70 + 130 = 200.

Week 3 (no supply event). Cumulative carries forward at 200.

The answer to "can we ship 150 by week 3" is yes, with 50 units to spare, because cumulative ATP reads 200 by week 3. And because the calculation already subtracted the 50 and 20 of existing firm orders, saying yes to this 150 does not put any of them at risk.

Reading a "no" and what to do about it

Now change the question: the customer wants 250 by week 3. Cumulative ATP is 200, so the honest answer is no, not at 250. The gap is 50 units. The calendar shows exactly where the shortfall bites, and there are two levers: add supply (firm a replenishment so a new receipt lands before week 3, lifting cumulative ATP) or move a commitment (delay a lower-priority firm order to free its share). Either lever changes the ATP column, and the salesperson can re-quote against the updated position.

If ATP is already negative in a bucket, the plant is oversold there before any new order arrives. The negative is not a blocked action; it is a visible signal that firm orders have outrun supply at that point. The fix is the same: add a receipt or relieve demand, then watch the column recover.

Why ATP starts from physical on-hand, not the window opening

One subtlety keeps the answer honest. ATP starts from physical on-hand now, the true ledger sum, not from the projection window's opening balance. If you open the calendar with a start date in the past, the window's opening reflects a historical position, but ATP always promises from current reality. This matters when a manager reviews last month alongside the forward plan: the promise math never quotes a stale starting point. The behavior traces straight to the inventory ledger, where on-hand is the authoritative sum.

Where ATP fits in the wider plan

ATP is the sales-facing face of the same planning layer that drives replenishment and finite capacity scheduling. When a promise cannot be met from stock, the shortfall becomes a build order that the engine schedules against real machine load, so a promised date is not just inventory-feasible but capacity-feasible. This is why EDGEBIC's planning connects to a production scheduling engine rather than stopping at an inventory forecast: the promise and the plan to fulfill it are one system.

For sales, the practical rule is short. Quote from cumulative ATP, not on-hand or projected balance. Read discrete ATP when you need to know which bucket is tight. And when the answer is no, use the calendar to see whether a receipt or a due-date change gets you to yes. That discipline is the difference between a promise the plant can keep and one it cannot, which is the same discipline behind sound inventory management for manufacturers.

See ATP answer live in the EDGEBIC platform overview, or contact US for a demo to test it against your order book.