Overhead is the part of a costing problem most likely to be marked wrong, because it is the only cost that is estimated. Direct materials and direct labor are traced from real documents; overhead is applied with a rate, and applied numbers drift. This guide shows the four places overhead allocation goes wrong, how to catch each one, and how to fix the year-end entry.
Why Overhead Allocation Goes Wrong in the First Place
Overhead is applied to jobs using a predetermined overhead rate, set before the year begins:
Predetermined overhead rate = Estimated total overhead ÷ Estimated total allocation base
Because both numbers in that fraction are estimates, the rate is an educated guess. Apply it across the year and the total overhead charged to jobs almost never equals the actual overhead the factory incurred. That difference is not a mistake — it is built into the method. The mistake is failing to reconcile it, or reconciling it the wrong way.
Two outcomes are possible at year-end. Underapplied overhead means you applied less than actual — too little overhead reached the jobs. Overapplied overhead means you applied more than actual. The Manufacturing Overhead account holds actual costs as debits and applied costs as credits; whichever side is larger names the problem.
The Four Places the Number Comes Out Wrong
When allocated overhead looks wrong on a problem, the cause is almost always one of these:
- Wrong allocation base in the rate. The estimated overhead is divided by the wrong base — labor dollars instead of labor hours, or machine hours instead of labor hours. Reread the problem; it tells you the base.
- Applying the rate to estimated activity instead of actual. The rate is set with estimated hours, but it is applied to each job's actual hours. Multiply the rate by estimated activity and every job is wrong.
- Including non-manufacturing costs in overhead. Sales salaries, office rent, and delivery are period costs, not manufacturing overhead. Sweep them into the overhead pool and the rate is inflated.
- Forgetting to reconcile at year-end. The applied total is left sitting against actual with no closing entry, so Cost of Goods Sold is misstated.
The first three corrupt the rate or its use; the fourth leaves a correct difference unresolved.
Catching It: The Diagnostic Check
Before fixing anything, confirm the direction and size of the error with a clean recomputation.
First, rebuild the rate from the estimated figures only and confirm the base matches what the problem specifies. Second, recompute applied overhead as rate × actual activity — actual hours or actual machine hours, job by job. Third, find actual overhead, which is the real total of indirect costs the factory incurred.
Now compare. If actual overhead is $310,000 and applied overhead is $295,000, overhead is underapplied by $15,000 — jobs were charged $15,000 too little. If applied were instead $322,000, overhead would be overapplied by $12,000. A quick sanity test: in the Manufacturing Overhead T-account, a leftover debit balance means underapplied, a leftover credit balance means overapplied.
Fixing the Year-End Entry
Once you know the amount and direction, the Manufacturing Overhead account must be closed to zero. For an immaterial difference, the standard fix is to close it directly to Cost of Goods Sold.
Underapplied overhead means COGS was understated — not enough cost flowed through — so COGS must go up. The entry debits Cost of Goods Sold and credits Manufacturing Overhead. For the $15,000 underapplied case: debit Cost of Goods Sold $15,000, credit Manufacturing Overhead $15,000.
Overapplied overhead means COGS was overstated, so COGS must come down. The entry debits Manufacturing Overhead and credits Cost of Goods Sold. For a $12,000 overapplied case: debit Manufacturing Overhead $12,000, credit Cost of Goods Sold $12,000.
If the difference is large, it is instead prorated across Work in Process, Finished Goods, and Cost of Goods Sold in proportion to the overhead in each — but for routine problems, closing to COGS is what is expected. The memory hook: underapplied adds to COGS, overapplied subtracts from it.
Getting Help
Overhead allocation errors usually surface inside a larger costing problem; if the cost flow itself is unclear, how job order costing works traces a full job from materials to finished cost. More managerial accounting troubleshooting lives in the Accounting study guides.
Conclusion
Fixing overhead allocation errors starts with accepting that an estimated rate will never match reality — the goal is a correct reconciliation, not a perfect rate. Check that the rate uses the right base, that it is applied to actual activity, and that only manufacturing costs are in the pool. Then identify under- or overapplied overhead and close it: underapplied raises Cost of Goods Sold, overapplied lowers it.
