Guide
What Over- and Under-Shipment Tolerance Should a Custom Parts Purchase Order Allow?
Over- and under-shipment tolerance is the band around the ordered quantity inside which a delivery still counts as complete, usually written as a percentage of the order line. For custom parts it matters because a supplier that ships 9,860 against 10,000, or 10,400, needs a clause that says whether that delivery is correct, short or excess before anyone argues about it.
By Saola Manufacturing engineering team · Published · Updated
General information, not legal advice. Have counsel review any clause before you rely on it.
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Why can a custom parts supplier not ship exactly the ordered quantity?
Because production yield is not perfectly predictable: parts are scrapped in the last operation, setup pieces are consumed, and cartons hold fixed counts. A tolerance admits that the supplier cannot hit the number exactly without either stopping short or over-making.
A shop that makes 10,000 parts typically starts the lot with a few more than 10,000 pieces of stock, because the first parts at a setup are adjusted and checked and some fail inspection after the final operation. If everything passes, the shop has more than ordered; if more than expected fail, it has fewer. Remaking a handful of pieces means a setup, a fixture change and a second inspection, so the cost of an exact count can be larger than the parts themselves.
Packing also moves the number. If a carton holds a fixed count, the last carton is either full or partly empty. Counting by weight, which is common for small parts, is an estimate that depends on the scale and the piece-weight sample. All three effects are the reason a purchase order should state a band, a rule for the surplus and a rule for the shortfall.
How is a shipping tolerance defined in purchase-order and ERP systems?
As a separate percentage for over-shipment and for under-shipment, applied to the quantity on the order line. The percentage is read against the ordered quantity, not against the shipped quantity, and a value of zero means no tolerance.
Oracle’s order-management documentation is a clear example. It treats the number you enter as a percent of the quantity ordered, says you cannot specify a fixed quantity tolerance, and keeps over-shipment and under-shipment as two parameters; the default is zero when no value is entered, and the under-shipment value must be less than 100 (Oracle Order Management 26A, 2026). The values can come from a default parameter or from the item record, and can be set separately for each business unit. The page’s own example enters 10 for each field on one item; that is a demonstration of how the field is filled, not a recommendation, and this guide does not suggest a band.
Invoicing is a second switch. In that documentation, a parameter decides whether an over-shipment is invoiced at the shipped quantity or the ordered quantity, with shipped quantity as the default; the page does not set a separate rule for under-shipments (Oracle Order Management 26A, 2026). The lesson for a purchase order is that three things must be written separately: the band, the delivery rule for what falls outside it, and the quantity that is paid for.
Do not assume that your own ERP behaves the same way. Check whether it measures the tolerance on the line, the release or the cumulative order, how it rounds, and whether the line closes automatically when a shipment lands inside the band.
Who decides whether the shipment is over or under?
The supplier decides what it ships, but the clause should say who has the option to accept or refuse what falls outside the band. Without that sentence, both sides can claim the choice.
Three practical allocations exist. In the first, the supplier may ship anywhere inside the band and the buyer must accept and pay for the actual count. In the second, the supplier may ship over but the buyer has the option to take or refuse the excess, at the buyer’s choice. In the third, the supplier may ship short but the buyer elects whether the balance is cancelled or shipped later.
For parts made to a drawing, the under-shipment rule usually matters more than the over-shipment rule, because a shortfall can stop an assembly line while an excess only occupies a shelf. A buyer may therefore want a narrower band for under-shipment than for over-shipment, or a notice requirement before shipping under; both are business decisions, and neither is recommended here. Say whether excess is returned at the supplier’s cost, kept at the unit price or held for the next release, and whether the supplier has to tell you when a lot will land outside the band before it ships.
How does the tolerance fit with UCC rules on lots and installments?
The UCC sets default rules for whether goods come in one delivery or in lots, and for when a nonconforming lot can be rejected, but it names no percentage band. The band is something you write into the contract.
Section 2-307 says that, unless otherwise agreed, goods under a contract for sale must be tendered in a single delivery and payment is due only on that tender, and that where the circumstances give either party the right to make or demand delivery in lots, the price may be demanded for each lot if it can be apportioned (UCC 2-307, Cornell LII, 2026). A contract that expects shipments in lots, such as a blanket order with releases, should say so explicitly.
Section 2-612 defines an installment contract as one that requires or authorizes delivery of goods in separate lots to be separately accepted, even if it calls each delivery a separate contract. A buyer may refuse an installment whose defect substantially impairs the value of that installment and cannot be cured, but must accept it if the seller gives adequate assurance of cure; and the whole contract is breached when defects in installments substantially impair its whole value (UCC 2-612, Cornell LII, 2026).
Read together, these sections suggest drafting for both a tolerance on each release and a cumulative tolerance on the order, so that a series of small surpluses or shortfalls does not drift away from the total. The sections cover defaults and remedies, so whether a given quantity variance is a breach depends on the wording of your agreement and the law that applies. That is a question for counsel. The guide on blanket purchase orders explains the release mechanics, and the guide on returning rejected parts covers the quality side.
How should the clause handle rounding, releases and invoicing?
Define the base, the rounding rule and the paid quantity in words, then test the clause with a worked example. A clause that cannot produce one number from an ordered quantity and a shipped quantity is not finished.
The worked example below shows how the same shipments are judged under different bands on a 10,000-piece line. It is arithmetic only. In a schedule-based system the quantities of the schedule lines normally sum to the ordered quantity, as the electronic purchase-order standard puts it for its schedule segment (Stedi X12 850 reference, 2026), so a band is a rule in the agreement and not a quantity that the transaction carries.
For small lots, a percentage can be less than one piece. Say whether the result is rounded up, down or to the nearest whole piece, and consider writing the band as the greater of a percentage or a fixed number of pieces. State whether the band applies to each release or to the cumulative total, how the counted quantity is verified (full count or counting by weight, and who owns the scale), and which quantity is invoiced.
| Shipped quantity | Share of order | Band: -1% / +1% | Band: -2% / +5% |
|---|---|---|---|
| 9,860 | 98.6% | Short by 40 below the 9,900 minimum | Inside the band (minimum 9,800) |
| 9,990 | 99.9% | Inside the band | Inside the band |
| 10,400 | 104.0% | Over by 300 above the 10,100 maximum | Inside the band (maximum 10,500) |
| 10,600 | 106.0% | Over by 500 | Over by 100 above the 10,500 maximum |
What should the drafting checklist contain?
A one-page list of defined terms: the base, the band, the rounding, the option, the invoice basis and the notice. When each is written down, the 9,860-against-10,000 argument becomes a lookup.
- Base: percent of the order line, release or cumulative order, stated once.
- Band: separate over and under values, or a fixed number of pieces where that is larger.
- Rounding: up, down or nearest whole piece, applied to the minimum and the maximum.
- Option: who may accept or refuse a shipment outside the band, and in what time after receipt.
- Shortfall: cancelled, back-ordered or at the buyer’s election, and the notice required before shipping short.
- Excess: returned, kept at the unit price or applied to the next release.
- Invoice basis: shipped quantity or ordered quantity, and what the packing list and invoice must show.
- Counting method: full count, or weight with a stated scale and piece-weight sample.
- Quality overlay: the band applies to conforming parts only; rejected parts do not count toward quantity.
Send the draft with the drawing and the expected release pattern when asking for a quote, so that the supplier can price in its yield rather than guess at it. Quotes for CNC turning and CNC milling are requested through the quote form; mention your tolerance and counting expectations there.
Frequently asked
Is a 10 percent tolerance standard?
No source reviewed for this guide treats it as a standard. The Oracle documentation uses 10 in an example, but it is a demonstration of the field, not a recommendation. The right band depends on the part, the yield and what an excess or shortfall costs you.
Should the tolerance be the same for over and under?
Not necessarily. A shortfall can stop your assembly, while an excess often only costs storage, so it can make sense to set the two separately.
Does the tolerance apply to each release or the whole order?
Say which. A per-release band alone allows small errors to accumulate; adding a cumulative band on the order keeps the total close to the order.
Do rejected parts count toward the quantity?
They should not. Write that the band applies to conforming parts and that a rejected quantity is replaced or credited separately.
Does the UCC give a standard percentage?
No. The sections reviewed here, 2-307 and 2-612, deal with delivery in lots and installment contracts, not a percentage band (UCC 2-307, Cornell LII, 2026). Have counsel review the clause.
Sources
- Set up shipping tolerances in Order Management, 26A, Oracle, 2026
- UCC 2-307 Delivery in single lot or several lots, Cornell Legal Information Institute, 2026
- UCC 2-612 Installment contract; breach, Cornell Legal Information Institute, 2026
- X12 850 Purchase Order, Stedi, 2026