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Everything so far has lived neatly inside your Ledger. But money doesn’t stay inside. It arrives from banks, card networks, and other systems, and it leaves to them too. So how does a self-contained Ledger connect to the world outside? And once it does, how do you prove your records still match what really happened out there? Two ideas answer this. Picture a building with a single front door. Everyone and everything coming in or going out passes through it. The door doesn’t store anything itself. It just marks the boundary between inside and outside. Your Ledger has a door like this.

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External accounts: the doorway to the outside

An external account is the doorway between your Ledger and the world beyond it: banks, card networks, other systems. Money entering your Ledger comes from an external account. Money leaving goes to one. Every crossing of your boundary passes through it. In Midaz, the default external account has debit direction. When R$100 flows in to a customer, Midaz uses that external account as the source. Its debit increases the available amount and balances the credit on the receiving account. The direction does not mean the external account has a negative balance.
Think of the building’s front door again. The external account is that door. Its direction tells Midaz how to apply a debit or credit. It does not label a balance as missing money.

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Reconciliation: proving the books match reality

Once you have a boundary, you need to check that what you recorded inside matches what the outside world recorded. That check is reconciliation: proving your internal records line up with external records (bank statements, processor reports, settlement files). You compare the two, line by line, and confirm they agree. When they don’t, reconciliation is how you catch it:
  • Missing movements: something happened outside that your Ledger never recorded.
  • Duplicated movements: the same thing recorded twice.
  • Mismatched movements: amounts or details that don’t line up.
The timing depends on your business: some reconcile continuously as records arrive, others at the end of each day. Either way, the moment you connect to the outside world, you take on the job of proving the two sides still agree.
Reconciliation is like counting the till against the receipts at the end of a shift. The cash drawer is your Ledger. The receipts are the outside record. Counting them against each other proves the books match what happened, and flags anything that doesn’t.

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Next steps

See it in LerianSee these ideas in practice: Transactions and the Glossary.