Money & WorkHow it works
How a 500-year-old technique catches its own errors.
In double-entry bookkeeping every transaction hits at least two accounts: once as a debit, once as a credit. The two totals must match. Profit is then derived twice – by comparing equity on the balance sheet and through the profit and loss account.
Useful: If the two routes disagree, there is an error somewhere – that mismatch is the system's built-in control.
Source: de.wikipedia.org