Double-entry bookkeeping

Every transaction touches at least two accounts, and the amounts recorded on the two sides are equal. A rupee that appears somewhere has to have come from somewhere, and the books force you to say where.

Kaveri Auto Components buys a lathe for ₹5,00,000 in cash. Machinery rises by ₹5,00,000; cash falls by ₹5,00,000. Total assets are unchanged, and nothing about the company's wealth has altered, because it swapped one asset for another.

Now buy the same lathe on credit. Machinery rises by ₹5,00,000 and trade payables rise by ₹5,00,000. Assets and liabilities both grew; the company is larger and more owed.

The vocabulary confuses more people than the concept does. A debit is not good and a credit is not bad; they are simply the left and the right of an entry, and which side increases an account depends on what kind of account it is. Assets and expenses increase on the left, liabilities, equity and income on the right. Once that is held, every transaction becomes a small puzzle with a checkable answer, and the reason accounts balance stops being a mystery and becomes a consequence of how each entry was written.

The discipline is 500 years old and its value is that an error has to be made twice to stay hidden.

Two sides, always. That is the whole system.