> ## Documentation Index > Fetch the complete documentation index at: https://docs.lerian.studio/llms.txt > Use this file to discover all available pages before exploring further. # Set up a ledger and post the first transaction (API) > From the organization and the ledger to a posted transaction and its balances, through the Midaz API. Create the ledger structure in Midaz, post the first transaction and read the result. ## Participants *** * **Your institution.** Your system. It calls the Midaz API. * **Midaz.** The ledger. It keeps the organizations, ledgers, assets, accounts, balances and transactions. ## Before you start *** * Your system has a token that can create organizations, ledgers, assets, accounts and transactions in Midaz. * Choose the code of the asset, for example `BRL`, and the alias of each account, for example `@customer-1`. ## Diagram *** ![Set up a ledger and post the first transaction](https://mintcdn.com/lerian-49cb71fc/KypD0TIKUCqZ014J/images/en/d2/id-midaz-create-and-transact.svg?fit=max\&auto=format\&n=KypD0TIKUCqZ014J\&q=85\&s=24984226ba40f215448c915faf5afd59) ## Steps through the API *** | # | From | To | Message | Lerian API | What happens | | - | - | - | - | - | - | | 1 | Your institution | Midaz | API call | [`POST /v2/organizations`](https://docs.lerian.studio/en/reference/products/midaz/v2/create-organization) | Create the organization with its `legalName` and `legalDocument`. Midaz answers `201` with the organization `id`. | | 2 | Your institution | Midaz | API call | [`POST /v2/organizations/{organization_id}/ledgers`](https://docs.lerian.studio/en/reference/products/midaz/v2/create-ledger) | Create the ledger with a `name`. Midaz answers `201` with the ledger `id`. | | 3 | Your institution | Midaz | API call | [`POST /v2/organizations/{organization_id}/ledgers/{ledger_id}/assets`](https://docs.lerian.studio/en/reference/products/midaz/v2/create-asset) | Create the asset with its `name`, `type` and `code`. | | 4 | Midaz | Midaz | Internal step | | Midaz creates the external account `@external/` of the asset when it does not exist yet. | | 5 | Your institution | Midaz | API call | [`POST /v2/organizations/{organization_id}/ledgers/{ledger_id}/accounts`](https://docs.lerian.studio/en/reference/products/midaz/v2/create-account) | Create the account with its `assetCode`, `type` and `alias`. Transactions find the account by its alias. | | 6 | Midaz | Midaz | Internal step | | Midaz creates the `default` balance of the account in the same call. | | 7 | Your institution | Midaz | API call | [`POST /v2/transactions/direct`](https://docs.lerian.studio/en/reference/products/midaz/v2/create-transaction-direct) | Post the transaction with its `asset`, `amount`, `debits` and `credits`. Each leg names the account `alias`, its `organizationId`, its `ledgerId` and its `amount`. Send the `X-Idempotency` header. | | 8 | Midaz | Midaz | Internal step | | Midaz debits each source balance and credits each destination balance. All of the balances change, or none of them changes. | | 9 | Midaz | Your institution | API answer | | Midaz answers `201` with the transaction and its operations. The status in this answer is `CREATED`. | | 10 | Your institution | Midaz | API call | [`GET /v2/organizations/{organization_id}/ledgers/{ledger_id}/accounts/alias/{alias}/balances`](https://docs.lerian.studio/en/reference/products/midaz/v2/get-balances-by-alias) | Read the balances of the account. | | 11 | Midaz | Your institution | API answer | | Midaz returns each balance of the account with its `available` and `onHold` amounts. | ## Rules *** * A debit is the account that the money leaves. A credit is the account that the money enters. The debits and the credits each total the transaction `amount`. * To bring value into the ledger, debit the external account `@external/` and credit your account. To send value out, debit your account and credit `@external/`. * When the Tracer mode of the ledger is `enforce`, Midaz refuses the transaction before it moves any balance if Tracer does not allow it. ## How you know it finished *** Read the transaction with [`GET /v2/organizations/{organization_id}/ledgers/{ledger_id}/transactions/{transaction_id}`](https://docs.lerian.studio/en/reference/products/midaz/v2/get-transaction). Its status is `APPROVED`. The balances of the source and destination accounts show the new amounts. ## What can go wrong *** | Situation | What you see | What to do | | - | - | - | | The asset of the account does not exist in the ledger | `404` with `0034` | Create the asset, then create the account. | | The debits or the credits do not total the amount | `422` with `0073` | Correct the amounts and send the transaction again. Midaz moved nothing. | | A source balance cannot cover its debit | `422` with `0018` | Add funds to the source, or post a smaller amount. Midaz moved nothing. | | You reuse an idempotency key for a different request | `409` with `0084` | Use a new key for each new transaction. | | You send the same request again before Midaz stores the result of the first | `409` with `0084` | Keep the key: the first request can still post the transaction. Send the same request again later with the same `X-Idempotency` key. | | The answer to the transaction does not arrive | No answer, or a timeout | Do not assume that the transaction failed. Within the time in the `X-TTL` header (300 seconds by default), send the same request with the same `X-Idempotency` key. A `201` with `X-Idempotency-Replayed: true` returns the first transaction. A `409` with `0084` means that Midaz has no stored result for the first request yet: send it again later with the same key. After that time, read the [operations of the source account](https://docs.lerian.studio/en/reference/products/midaz/v2/get-all-operations-by-account.md) before you send the transaction again. | ## Related *** * [Reserve an amount, then confirm or cancel](https://docs.lerian.studio/en/diagrams/lerian-products/midaz-reserve-then-confirm-or-cancel.md) * [Reverse a transaction](https://docs.lerian.studio/en/diagrams/lerian-products/midaz-reverse-a-transaction.md) * [Charge a fee on a transaction](https://docs.lerian.studio/en/diagrams/lerian-products/midaz-charge-a-fee.md) * [Register a holder and open an account](https://docs.lerian.studio/en/diagrams/lerian-products/midaz-register-a-holder.md) * [Midaz error list](https://docs.lerian.studio/en/reference/products/midaz/error-list.md) This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.