Prior Period vs. Same Period Last Year: How to Compare Financial Results
Check accounting periods and comparative reporting dates before calculating growth. Learn how fiscal year changes, seasonality, and restated comparatives can distort comparisons.
Prior period refers to the immediately preceding accounting period or the previous period identified in the statement; it does not always mean the same quarter a year earlier. Balance sheets compare specific reporting dates, while income and cash flow statements compare periods with start and end dates. Check the actual dates and period lengths before relying on headings such as current and prior period.
Separate balance comparisons from performance comparisons
A quarterly balance sheet may show the previous year-end balance as its comparative, but that is not the same time frame as the income statement's same-period-last-year results. Inventory increasing from the previous year-end and revenue increasing year over year use different comparison axes. To connect the movements, you can also examine balances at the same quarter-end a year earlier to account for seasonality. In tables, write the reporting date or start and end dates rather than labeling columns only current and prior period.
Count the months first when the fiscal year changes
A company's fiscal year may differ from the January-to-December calendar year. If the year-end changes or a short accounting period is presented, check how many months each comparative period covers. Higher revenue over a longer period does not by itself establish growth. A simple monthly average can provide a supplementary comparison, but does not resolve seasonality or differences in working days. For overseas companies using week-based fiscal years, also check the actual period lengths and compare similar seasonal intervals.
Document the latest basis when comparative figures change
Prior-period comparatives may be restated because of accounting policy changes, material error corrections, or other reasons. If figures saved from the original release differ from the latest report's prior-period figures, read the restatement explanation rather than choosing whichever value is convenient. An estimate change may result from new information and should be distinguished from correction of a past error. Label figures as originally reported or restated comparatives, and record why the selected scope is comparable with the current period so the growth calculation can be reproduced later.
Worked example
Hypothetical example: All amounts below are in units of KRW 100 million. A prior reporting period covering 9 months has revenue of 900, while the current period covering 12 months has revenue of 1,200. The totals alone show an increase of 33.3%, but the simple monthly average is 100 in both periods. This does not conclusively establish actual growth of 0%, because the missing 3 months may have been a peak or off-peak season. For an appropriate comparison, seek revenue covering the same months or comparable data supplied by the company. If unavailable, disclose the limitation created by different period lengths.
What to check
- Distinguish headings for point-in-time balances from those for period totals.
- Record start and end dates for both the current and prior periods.
- Check fiscal year changes and differences in period length.
- Record whether the latest report uses restated comparatives.
Sources and primary materials
This is educational material about research methods. For an actual company decision, verify the filings and primary sources for the relevant period.