How to Reconcile Accumulated Amortization to the General Ledger

Accumulated amortization is a contra-asset account, and it misbehaves in predictable ways. The subledger tracks it asset by asset, while the G/L holds one lump. This article walks through the reconciliation that proves the two agree.

What is the reconciliation trying to prove?

You are showing that the accumulated amortization balance in the G/L equals the sum of the per-asset accumulated amortization in the fixed asset register. The standard proof is a roll-forward:

• Opening balance, per asset or per G/L account
• Plus amortization expense posted in the period
• Less amortization removed on disposals
• Equals closing balance

If the closing balance ties to the G/L, the subledger and the ledger agree. If it does not, the difference tells you where to look.

Prepare the subledger first

Before you print or export anything, tidy the register. Each asset needs a complete description, an in-service date, a method and useful life, and the correct G/L account mapping. An asset with no account code will drop out of the grouping entirely, and that is the most common source of a difference.

Group assets by their accumulated amortization G/L account, not by class or tax category. Tax-basis amortization often differs from book, so confirm you are reporting on the book basis unless the reconciliation is specifically for tax.

Work the roll-forward

Take a simple example. An asset class opens the year with 40,000 of accumulated amortization. Current-year expense adds 10,000. One asset with 6,000 of accumulated amortization is sold, and its cost and accumulated amortization come off the books through the disposal entry. The closing balance is 44,000.

Now check the G/L. If the accumulated amortization account shows 50,000, the disposals were never posted to it: the sale removed cost but left the contra balance behind, overstating accumulated amortization and misstating the gain or loss. If it shows 40,000, the depreciation journal for the year was never posted. The direction of the difference points at the missing entry.

Review the columns

Most registers produce a report with the same shape. Read each column with a question in mind:

• Opening balance: does it agree to last year's reconciled closing balance? If not, something was posted directly to the G/L account after you last tied it out.
• Additions: does the total agree to the amortization expense posted for the period? It should, to the penny.
• Deletions: does each one trace to a disposal entry that also relieved cost? A deletion without a matching cost entry, or the reverse, breaks both sides of the asset section.
• Closing balance: does it tie to the G/L trial balance?

The judgement calls

Watch for direct journal entries to the accumulated amortization account. Nothing should ever post there except the periodic depreciation entry and disposals. A "correction" posted straight to the G/L will not appear in the subledger, and the two will drift apart until someone finds it.

Watch for assets disposed of mid-period where amortization was taken for the full month, or none at all. Policy usually sets a half-month or full-month convention; apply it consistently in both the register and the journal.

Finally, keep the reconciliation as a working paper. A one-page roll-forward, signed off each period, turns a year-end scramble into a five-minute check.