SingaporeBusiness StudiesSyllabus dot point

How much stock should a business hold, and how do the choices of suppliers and stock systems affect its costs and reliability?

Explain how a business manages inventory, including stock control, reorder and buffer levels, just-in-time, and the importance of choosing reliable suppliers

A focused answer to the O-Level Business Studies outcome on inventory and supply. Stock control with reorder and buffer levels, just-in-time versus just-in-case, and the importance of choosing reliable suppliers.

Generated by Claude Opus 4.88 min answerUpdated 2026-06-06

Reviewed by: AI editorial process; not yet individually human-reviewed

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The answer
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What this dot point is asking

This outcome wants you to explain how a business manages inventory (stock): the idea of stock control with reorder and buffer levels, the just-in-time (JIT) approach compared with holding stock just-in-case, and why choosing reliable suppliers matters. The central idea is that holding stock involves a trade-off: too much ties up cash and risks waste, while too little risks running out and halting production or sales.

The answer

Why inventory management matters

Inventory (stock) includes raw materials, work-in-progress and finished goods. Managing it well matters because:

Too much stock ties up cash, raises storage costs, and risks goods becoming damaged or out of date.
Too little stock risks stock-outs, stopping production or losing sales and customers.

The aim is to hold enough stock to meet demand without holding too much.

Stock control levels

A simple stock-control system uses key levels:

Maximum stock level - the most the firm will hold (limited by storage space and cash).
Reorder level - the level at which a new order is placed, set so the delivery arrives before stock runs too low.
Buffer (minimum) stock level - a safety reserve kept in case of delays or sudden demand, not normally used up.
Lead time - the gap between ordering and delivery; longer lead times need a higher reorder level.

Just-in-time and just-in-case

Just-in-case (JIC) holds buffer stocks so the firm can cope with surprises. It is safer but ties up cash and storage.
Just-in-time (JIT) holds little or no stock; materials arrive just as they are needed. It cuts storage costs, frees cash and reduces waste, but depends completely on reliable, fast suppliers, so any delay can stop production.

Choosing reliable suppliers

A good supplier matters for cost and reliability. Firms judge suppliers on:

Price - cost per unit and discounts.
Quality - consistent, fit-for-purpose materials.
Reliability - delivering the right amount on time, every time.
Flexibility and lead time - coping with changes in order size.

Reliable suppliers are essential for JIT, because there is no buffer to fall back on if a delivery fails.

Worked example

A workshop uses 60 units of material a day. Its supplier's lead time is 4 days, and it wants a buffer stock of 100 units. Work through the reorder level and check what happens during the lead time.

Step 1: Work out usage during the lead time

Daily usage is 60 units and lead time is 4 days, so usage while waiting for delivery is $60 \times 4 = 240$ units.

Step 2: Set the reorder level

The reorder level must cover usage during the lead time plus the buffer it wants to keep: $240 + 100 = 340$ units. So the workshop should reorder when stock falls to 340 units.

Step 3: Check the logic

Ordering at 340 units, the firm uses 240 units over the 4-day lead time, leaving exactly the 100-unit buffer when the delivery arrives, so it never breaks into the safety reserve under normal conditions. If the supplier is sometimes late or demand rises, the buffer protects production, which is why a firm with unreliable suppliers should keep a larger buffer rather than move to pure just-in-time.

Examples in context

Example 1. A car plant using JIT. A car manufacturer in the region uses just-in-time: parts arrive from suppliers only hours before they are fitted, so the plant holds almost no stock. This frees enormous amounts of cash and storage space and avoids waste. The trade-off is total reliance on supplier reliability and transport, so when a key supplier was once disrupted, the line had to stop within a day - showing both the saving and the risk of JIT.

Example 2. A supermarket's stock control. A Singapore supermarket sets reorder and buffer levels for each product, using sales data to reorder fast-selling lines automatically before they run out, while keeping a small buffer for sudden demand. Fresh goods are kept low to avoid spoilage, while long-life goods can be held in larger amounts. This shows stock control tailored to the product, balancing the cost of holding stock against the risk of empty shelves.

Try this

Q1. Define the term buffer stock. [2 marks]

Cue. Buffer (minimum) stock is a reserve of stock a business keeps as a safety margin, held in case of unexpected demand or delivery delays so it does not run out.

Q2. State two benefits to a business of using a just-in-time stock system. [2 marks]

Cue. Any two of: lower storage costs, less cash tied up in stock (better cash flow), and less waste from damaged or out-of-date goods.

Q3. Explain one reason why choosing a reliable supplier is important for a business using just-in-time. [4 marks]

Cue. Under just-in-time the firm holds little or no buffer stock, so it depends on materials arriving exactly when needed. If a supplier is unreliable and a delivery is late or wrong, there is no spare stock to fall back on, so production stops, orders are missed and customers may be lost. A reliable supplier that delivers the right quantity and quality on time is therefore essential to keep production running smoothly without a buffer.

Exam-style practice questions

Practice questions written in the style of SEAB exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.

Original4 marksExplain what is meant by the buffer (minimum) stock level and the reorder level in stock control.

Show worked answer →

Buffer (minimum) stock level is the lowest amount of stock a business plans to hold as a safety reserve, kept in case of unexpected demand or delivery delays so the firm does not run out.

Reorder level is the stock level at which a new order is placed, set high enough that the delivery arrives before stock falls to the buffer level.

The key idea is that the reorder level triggers a new order, and the buffer level is the safety cushion that should not normally be used up.

What markers reward: a correct definition of each term and the link between them - reorder triggers ordering, buffer is the safety reserve that protects against running out.

Original6 marksA manufacturer is considering switching from holding large stocks (just-in-case) to a just-in-time system. Analyse two benefits and one risk of just-in-time.

Show worked answer →

Benefit 1 - lower storage costs and less cash tied up. With little stock held, the firm spends less on warehousing and frees up cash that would otherwise sit in inventory, improving cash flow.

Benefit 2 - less waste. Holding little stock means fewer goods become damaged, out of date or obsolete, cutting waste costs.

Risk - vulnerability to supply problems. With no buffer, any delivery delay, supplier failure or sudden demand spike can halt production, because there is no spare stock to fall back on.

Develop the chain: JIT cuts storage and waste costs and frees cash, but relies completely on reliable suppliers and fast delivery, so a single disruption can stop output.

What markers reward: two developed benefits (lower storage cost, less cash tied up, less waste) and one developed risk (supply disruption with no buffer), applied to the manufacturer.