[Glossary](https://blnkfinance.com/glossary) Ledger # What is a ledger? Ledger A ledger is the system of record for money in a product. It stores balances and the transactions that change them. Banks, wallets, and marketplaces each have one, even when they also use a bank. The bank statement is not the product’s book. ## How does a ledger work? You open balances for each store of value. You post transactions that move value between them. The current balance is the sum of those posts. If a number is not in the ledger, it is not in the product. Spreadsheets and processor dashboards are copies. ## Ledger vs bank account A bank account is one balance at a bank. A ledger is the set of all balances you owe an explanation for: customers, fees, revenue, clearing, escrow. The bank account is often the omnibus behind many ledger balances. They must reconcile. They are not the same object. ## When do you need a ledger? When more than one party can hold a balance, when you take a fee, when money sits between rails, or when a regulator asks who owns what. If you only forward card charges and never hold a balance, you may not need one yet. Most products that say “wallet” already do. Blnk Core is an open-source double-entry ledger. You group balances into ledgers, post source-to-destination transactions, and treat that book as the system of record. Cloud sits on the same book. See [ledgers](https://docs.blnkfinance.com/ledgers/introduction). Related terms - [Double-entry](https://blnkfinance.com/glossary/double-entry) - [Balance](https://blnkfinance.com/glossary/balance) - [Transaction](https://blnkfinance.com/glossary/transaction) - [General ledger](https://blnkfinance.com/glossary/general-ledger)