Use flow time to explain cash tied up in unfinished work

A business can complete a steady number of customer cases while carrying a large amount of unfinished work. The difference often lies in how long each case remains inside the process, including time waiting for approvals or the next available specialist.

MIT's Lean Thinking materials present Little's Law as a relationship between average work in progress, average throughput rate and average flow time. With consistent boundaries and an appropriate stable operating view, average work in progress equals throughput multiplied by time in the system.

Finance can use that relationship to examine operating cash exposure, but the physical count is not automatically an accounting asset balance. The financial conversion requires separate evidence about when spending occurs, how much is invested in each case and when cash is recovered.

Define when a case enters and exits the process. For example, entry might be release to delivery after the required customer information is complete, and exit might be accepted completion. Starting the clock at the first sales inquiry would include a different population and different waiting time.

Use the same boundary for the open-case count, throughput and elapsed time. Count cases in the system, measure completed cases per week and measure weeks between the defined entry and exit. Mixing daily throughput with a weekly time measure requires a conversion before multiplication.

Specify how cancellations and returns are handled. A canceled case leaves the operating queue even if it does not produce ordinary revenue. Excluding such exits from the flow calculation while removing them from the open count can make the measures inconsistent.

Assume an invented stable process completes 50 comparable cases per week, with an average flow time of four weeks. Its average unfinished population is 200 cases. Now assume $600 of cash is paid at entry for every case and that this funded amount is recovered only when the case exits successfully.

Under those deliberately simplified funding assumptions, average cash invested in unfinished work is $120,000. If flow time falls to three weeks while throughput remains 50 cases per week, average unfinished work falls to 150 cases and the corresponding investment falls to $90,000.

The modeled reduction is 50 cases and $30,000 of cash tied up. This is an operating investment comparison under stated timing assumptions. It does not establish the value at which work should appear in the financial statements or imply that every business funds its work at the start.

Reducing the steady amount invested by $30,000 can release cash as the process transitions. It is not a fresh $30,000 profit or cash saving every month. Once the lower unfinished-work level is established, sustaining it preserves the lower funding requirement.

There may be recurring benefits from lower financing cost, reduced storage or fewer errors, but calculate those separately from evidence. A reduction in elapsed waiting time does not automatically reduce paid labor hours. Staff can remain equally busy while cases spend less time queued between activities.

The transition itself needs a cash schedule. Clearing old work, changing the release policy or temporarily adding capacity can require spending before the lower steady-state investment is reached. Show that path rather than assume the full modeled cash release appears immediately.

If spending accumulates gradually, $600 per open case overstates early-stage investment and may understate later-stage investment. Use the stage-specific cash already paid or a supported average investment profile. A mixed queue with very different case values needs more than a single unweighted count.

Customer deposits can fund part of the work, while supplier credit can delay the business's payment. Include those arrangements when estimating net cash invested. Keep operational work count separate from the financing terms that change its cash consequence.

If cash is collected after completion, the receivable period sits outside the chosen delivery boundary. A faster process may move invoicing earlier, but the full cash conversion still includes collection time. Extend the boundary or add the receivables schedule explicitly instead of assuming completion equals payment.

A rapidly growing backlog is not a stable system with balanced inflow and outflow. Dividing today's open work by last week's completions can provide a rough indicator, but it is not automatically a reliable estimate of future individual flow time. Review the release and completion pattern over an appropriate period.

Use comparable averages and allow for cases crossing the observation window. Measuring elapsed time only for quickly completed cases while ignoring older unfinished work can make the reported process look faster than it is. Retain the age distribution of the open queue alongside completed-case times.

Different case classes may need separate analysis. Routine work and complex exceptions can have different funding and time profiles. An aggregate average can conceal a small group that holds a large share of the cash investment.

Map where time accumulates before proposing a lower target. Missing customer information, batched approvals and specialist bottlenecks need different remedies. Little's Law describes the relationship among the averages; it does not establish that any one input can be changed independently at will.

A lower release rate can reduce open work temporarily but may also reduce throughput if the process becomes starved. Removing necessary review can accelerate completion while creating costly rework. Evaluate the operating change and its service consequences rather than treating a smaller queue as sufficient proof of improvement.

After the change, measure throughput, flow time, unfinished cases and the associated cash records together. The result should show whether the business delivers the same useful output with less money waiting inside the process, and what it cost to make that improvement happen.