Flux analysis in accounting: Thresholds, examples, and how to explain changes

Flux analysis, short for fluctuation analysis, compares account balances between two periods, flags changes that pass a materiality threshold, and documents the reason for each one. Accounting teams run it during the month-end close to confirm that balances make sense before financial statements go to leadership.

• FluxThe change in an account balance between two periods, shown in dollars and as a percentage
• ThresholdThe dollar and percentage change that triggers a written explanation
• Flux commentaryThe written explanation of what changed, why, and by how much

The same discipline shows up in finance beyond the close. SEC Regulation S-K Item 303 requires public companies to explain material changes in line items from period to period. That includes changes that offset each other within a line item. The rule adds that the discussion “must not merely repeat numerical data.” Flux commentary written well during the close becomes the raw material for that discussion.

Knowing which comparison you're running tells you which question the explanation has to answer. Flux analysis compares actual results with actual results from an earlier period, while variance analysis compares actual results with a budget, forecast, or target. Some teams and vendors use the two terms interchangeably, so check the baseline before you read a report.

A line can pass one test and fail the other. Say revenue rises 8% month over month but lands 5% below budget. The flux note covers the new contracts behind the increase, and the variance note covers the deals that slipped. For the budget side, see budget vs actual.

Running flux at the right point in the close means you fix errors before they reach the financial statements instead of explaining them afterward. Flux analysis comes after subledgers are closed, accounts are reconciled, and accruals are posted, and before the controller signs off and the period locks.

1. 1Close subledgers and post entriesPayables, receivables, payroll, fixed assets, accruals, prepaids, and reclasses
2. 2Reconcile balance sheet accountsTie each balance to bank statements, subledgers, and schedules
3. 3Run flux analysisCompare the trial balance with prior periods, flag what passes the threshold, and investigate
4. 4Post corrections and refreshBook the adjusting entries the investigation finds, then rerun flux on the updated trial balance
5. 5Review and sign offA reviewer approves each explanation before the period locks

Many teams run a preliminary flux a day or two before the final one, so large surprises surface while there's still time to fix them. Flux runs every month as part of the close, and again at quarter-end and year-end for reporting and the audit. For the full sequence, see the month-end close process.

Flux works alongside reconciliation and doesn't replace it. A balance that has been wrong for six months shows no movement, so it passes every flux threshold. Account reconciliation is what proves the balance itself is right.

Splitting flux by statement helps you pick the right comparison and threshold for each account. Income statement flux looks at activity during the period. Balance sheet flux looks at balances at a point in time and asks whether the roll-forward makes sense.

Accruals and prepaids often start from small or zero balances, so a modest dollar change can read as a 200% increase. A dollar-only rule works better for those accounts, as the threshold section below explains.

The flux analysis formula gives you two numbers for every account: the size of the change and its size relative to the starting balance.

• Dollar changeCurrent period balance − Prior period balance
• Percentage change(Current period balance − Prior period balance) ÷ |Prior period balance| × 100

Use the absolute value of the prior balance so liabilities and other credit balances show the right direction. When the prior balance is zero, the percentage can't be calculated, so the dollar rule decides whether the account needs an explanation.

A repeatable process keeps the work consistent from month to month and makes each preparer's commentary faster to review.

1. 1Pull the trial balance for both periodsUse the same account mapping for each, so a reclass or new account doesn't show up as a false change.
2. 2Calculate dollar and percentage changesRun the comparison for each entity and on a consolidated basis.
3. 3Apply your threshold rulesFlag every account that passes the dual threshold, the override, or the always-review list.
4. 4Investigate the driversOpen the general ledger detail behind each flagged account, starting with the largest entries and anything new this month.
5. 5Put an amount on each driverThe drivers should add up to the total change, and anything left over is a residual that needs more work.
6. 6Fix what's wrongPost a correcting entry for any error the investigation finds, then refresh the comparison.
7. 7Write the commentary and attach supportReference the invoice, contract, payroll register, or schedule behind each driver.
8. 8Send it for reviewA reviewer who didn't prepare the analysis checks each explanation against its support and signs off.

Thresholds decide how much of your close goes into flux, so setting them well is the fastest way to make the review shorter and sharper. A single percentage rule, such as 5%, flags small accounts that move a few hundred dollars. It also misses large accounts that move a lot of money at a low percentage. On Reddit's r/Accounting, one accountant described submitting the team's eighth flux, comparing the current year with both plan and prior year.

Use three rules together:

• Dual thresholdFlag an account when the change passes both a dollar amount and a percentage, which removes small-dollar noise.
• Dollar overrideFlag any change above a larger dollar amount, whatever the percentage, which catches big moves in large accounts such as payroll and revenue.
• Always-review listReview intercompany, suspense and clearing accounts, equity, and any account hit by an unusual manual journal entry every month, regardless of size.

The table below is an illustrative starting point for a company with about $50 million in annual revenue. Scale the dollar amounts to your own materiality.

Test thresholds before you adopt them. Apply two or three candidate rule sets to last month's trial balance and count how many accounts each one flags. Pick the set your team can investigate properly in the time the close allows. Revisit the rules after two or three closes.

If your flux review is a SOX control, the thresholds also need to be precise enough to catch a material error. KPMG's 2025 guide on control precision defines precision as the size of misstatement a control would prevent, or detect and correct, on a timely basis. Agree the thresholds with your auditors so they can rely on the review.

A worked example shows how the formula, thresholds, and commentary come together in one close.

Payroll's 6.4% increase would not pass a 10% rule on its own, so the $100,000 override is what puts it on the list. Travel rose 22.6%, but the $7,000 change is below the dollar threshold.

Here's the commentary for each flagged account.

Subscription revenue, +$320,000 (+7.6%): Three new customers began billing in October ($210,000), a 5% price increase on renewals took effect October 1 ($95,000), and usage overages added $15,000. New customer and price revenue will recur, while overages vary with usage. Support: October billing register and signed order forms.

Payroll and benefits, +$118,000 (+6.4%): Nine new hires started October 1 ($81,000) and annual merit increases took effect the same day ($52,000), partly offset by a lower sales commission accrual (−$15,000). Both main drivers will recur. Support: payroll register and headcount report.

Software and subscriptions, +$35,000 (+40.7%): A $36,000 annual data platform renewal was posted in full to expense, $4,000 came from new design tool seats, and a cancelled analytics tool saved $5,000. The renewal covers October through September, so it belongs in prepaid expenses. The preparer posted this correcting entry, which keeps October's $3,000 share ($36,000 ÷ 12) in expense:

After the correction, October software expense is $88,000, up $2,000 (2.3%) from September and below the threshold. Prepaid expenses rise to $245,000.

Prepaid expenses, +$181,000 after correction: The annual insurance renewal paid October 1 added $180,000, less $15,000 of October amortization. The data platform renewal reclassified from expense added $33,000, less $17,000 of amortization on existing prepaids. Support: insurance invoice, renewal order form, and prepaid schedule.

Accrued expenses, −$58,000 (−14.1%): September's $70,000 legal fee accrual reversed on October 1 after the invoice arrived and was posted to accounts payable. A new $12,000 accrual for audit fieldwork performed in October partly offsets it. Spending didn't fall: the legal liability moved from accrued expenses to payables.

A weak note on software would have said “Software expense increased due to higher software costs.” It repeats the number and misses a $33,000 error.

Clear commentary lets a reviewer approve a flagged account without sending questions back to the preparer. Harvard's Office of the Controller lists four parts of a good flux explanation. They are what changed, why it changed, the amount of each part of the change, and wording a third party with accounting knowledge can follow.

Check every note against four tests before it goes to review:

• Drivers add upThe amounts sum to the total change, or the note states the residual.
• Recurrence is labeledEach driver is marked recurring, one-time, timing, or error.
• Support is namedThe note references an invoice, contract, register, or schedule a reviewer can open.
• Wording is plainNo internal shorthand that a new team member or an auditor wouldn't know.

Some of the largest swings in a flux come from accounting mechanics, and explaining them as business changes misleads leadership. Separate these effects before you write the commentary.

• FX revaluation and translationBalances held in a foreign currency change when exchange rates move, even when activity is flat. Split the change into the currency effect and the underlying activity, or compare both periods at the same rate.
• Accrual reversalsAn accrual booked at month-end and reversed on the first day of the next month makes one month look high and the next look low. Read the accrual and the matching invoice together, as in the legal fee example above.
• Cut-off errorsAn invoice or shipment recorded in the wrong month moves activity between periods. Correct it in the right period when it's material, and note it in the commentary when it isn't.
• Reclasses and mapping changesMoving costs between accounts or departments creates two offsetting changes, so explain both sides together.
• Offsetting activityAn account can show a small net change while large debits and credits cancel out, such as a duplicate entry and its reversal. For high-risk accounts, review the activity as well as the ending balance.

For how reversing entries work, see adjusting entries.

Good documentation lets auditors rely on your flux review instead of rebuilding it. When auditors use analytical procedures as a substantive test, PCAOB AS 2305 has them develop an expectation, compare it with the recorded amount, and investigate significant differences. The standard says management's explanations should ordinarily be corroborated with other evidence, so commentary without support carries little weight.

AS 2305 also says monthly comparisons, and comparisons by location or line of business, generally catch misstatements better than annual, company-wide ones. For a multi-entity company, that means running flux for each entity, not only on consolidated numbers where offsetting moves can hide. The AICPA's AU-C section 520 covers the same ground for audits of private companies.

A flux file ready for audit review holds:

• The comparison basis and thresholds, written down and applied the same way every month
• Each flagged account with its quantified drivers and support
• The correcting entries the review produced
• Preparer and reviewer names and dates, with the reviewer separate from the preparer
• Evidence that the reviewer challenged weak explanations, such as notes or items sent back

Clear ownership keeps flux from becoming a last-day scramble and gives every flagged account one accountable person.

For a company with several entities and a few hundred accounts, assign each account an owner and a risk level. Run flux by entity and consolidated, and keep the always-review list short. A preparer should never approve their own explanation or the correcting entry that came out of it.

Your ERP already has comparison reports, so you can start without a separate tool and export to a spreadsheet for the threshold logic.

• NetSuiteGo to Reports > Financial > Comparative Income Statement to compare two or more periods side by side. NetSuite's 2026.2 release, announced July 15, 2026, added Intelligent Flux Analysis, which uses AI to draft explanations for balance changes from the Comparative Income Statement or as a task in the Intelligent Close Manager portlet.
• Sage IntacctGo to Reports > All > Core > Financial reports, open the report, select Edit, and use the Columns tab to set reporting periods relative to the as-of date. The Expand by option splits a period into months or compares dimensions such as department or location.
• QuickBooks OnlineGo to Reports > Standard reports and run Profit and Loss Comparison, or use Compare to add Previous period (PP) or Previous year (PY). Under Calculations, add $ change and % change.

A consistent template makes every preparer's work look the same, which speeds up review. Use these columns in Excel or in your close tool.

The IFERROR treats a zero prior balance as a 100% change, so the dollar rule decides whether the account is flagged.

Automated flux analysis now handles most of the mechanical work, which frees your team's time for judgment. Calculating changes, applying thresholds, pulling the transactions behind a flagged account, and drafting a first explanation can all be automated. A person still needs to confirm the business reason, check that every number in the draft ties to the ledger, decide whether a driver will recur, and sign off.

Treat an AI draft the way you'd treat a new preparer's draft. Check that the drivers add up, that each one points to real support, and that the draft says “unexplained” when the data doesn't show a cause instead of guessing. For close tools with flux features, see best month-end close software.

We also build AI agents for this work. Our FP&A Agent investigates variances across your connected systems, separates recurring from one-off effects, and drafts the explanation for your team to review, on top of your existing ERP. If you want to see how it fits your close, explore our FP&A Agent.