Why your P&L and balance sheet should reconcile every month
Ask most business owners whether their profit and loss is right and they will say yes. Ask whether it reconciles to the balance sheet and the answer is usually a pause. The two statements are not independent reports. They are two views of the same ledger, and if they do not agree, at least one of them is wrong.
The relationship
Every transaction touches both statements. An invoice raised increases revenue on the P&L and receivables on the balance sheet. A wage paid increases expenses and reduces cash. So over any period, the profit on the P&L must equal the movement in net assets on the balance sheet, after allowing for money the owners put in or took out. Opening net assets, plus profit, plus contributions, less drawings, equals closing net assets. That is the whole test.
What it catches
When the test fails, the usual causes are mundane and expensive. Depreciation that stopped being posted part way through the year, so assets are overstated and profit is flattered. Costs capitalised that should have been expensed, which makes the margin look better than it is. A bank feed that was reconciled to the statement but coded to the wrong account. A loan repayment posted to interest instead of principal. Journals entered in the P&L with no balance sheet side, or the other way around. Each of these produces a P&L that looks reasonable on its own and is wrong.
We have seen a business run for the best part of a year on a gross margin that was several points too high, because hosting costs were sitting on the balance sheet. The board was making pricing decisions on it. A monthly reconciliation would have caught it in month one.
Why monthly
An annual reconciliation is what your accountant does at year end, and by then the decisions have been made. A monthly one costs a few minutes once it is built into the pack, and it turns the year-end from a correction exercise into a confirmation. It also means the numbers the board saw in March are the same numbers the accountant signs off in September, which is the only sensible definition of a reliable management pack.
How to build it in
Put the reconciliation on the same page as the balance sheet, one line per month: opening net assets, profit for the month, owner movements, closing net assets, and a difference column that should read zero. If the difference is not zero, do not publish the pack until it is. That rule alone changes the quality of the ledger, because errors get found by the person who made them, a few days after they made them, rather than by an auditor a year later.
The wider point
A pack that reconciles is not a nice to have. It is the difference between reporting and bookkeeping output. Directors are entitled to rely on the numbers they are given, and the only way to give them that entitlement is to prove, every month, that the two statements agree.
