diff --git a/Documentation/cli.md b/Documentation/cli.md
new file mode 100644
index 0000000..852b003
--- /dev/null
+++ b/Documentation/cli.md
@@ -0,0 +1,101 @@
+## Command structure
+```
+rpnc
+├── batch
+│   ├── update       # 1. Recalculate all values of batch using data from transactions table
+│   │                # 2. Update batch values
+│   └── list         # list all batches in DB
+│
+├── card
+│   ├── create       # add card to DB
+│   │                #   - require customer
+│   │                #   - require status
+│   │                #   - require description
+│   │                #   - require pin
+│   ├── read         # fetch card details
+│   ├── update       # modify card
+│   ├── delete       # delete card
+│   │                #   only allowed on cards not referenced by any transactions 
+│   └── list         # list all cards
+│                    #   allow filtering by customer, status
+│
+├── customer
+│   ├── create       # add customer
+│   │                #   - require customer number (ID) and name
+│   ├── read         # fetch customer details
+│   ├── update       # modify customer
+│   ├── delete       # delete customer
+│   │                #   only allowed on customers not referenced by any transactions 
+│   └── list         # list all customers
+│
+├── daemon
+│   ├── start        # start the web server daemon
+│   ├── status       # check status of daemon
+│   │                #   - running?
+│   │                #   - port?
+│   │                #   - db access?
+│   │                #   - accessible from internet?
+│   │                #   - fqdn?
+│   └── stop         # stop daemon
+│
+├── db
+│   ├── setup        # create database and schema
+│   ├── reset        # drop and recreate database
+│   ├── status       # check if connection to db is ok
+│   ├── backup       # create a backup of database
+│   └── restore      # recreate database from backup
+│
+├── file
+│   ├── import       # read CSV into DB:
+│   │                #   1. create any missing customers
+│   │                #   2. create any missing cards
+│   │                #   3. create transactions
+│   │                #   4. create any missing batches
+│   │                #   5. verify batch values match calculated value
+│   ├── list         # list all files stored in DB
+│   └── export       # export file to specified format
+│
+├── invoice
+│   ├── create       # add invoice to DB:
+│   │                #   - require batch OR date range
+│   │                #   - require "all" or specific customer
+│   ├── read         # fetch invoice details
+│   ├── update       # modify invoice
+│   │                #   - only allowed on invoices with "draft" status
+│   ├── delete       # delete invoice
+│   │                #   - only allowed on invoice with the highest ID number
+│   │                #   - only allowed if invoice status is "draft"
+│   ├── credit       # create a credit invoice
+│   │                #   - required if errors is needed to be fixed on a sent invoice
+│   ├── export       # write HTML files to disk
+│   └── list         # list all invoices
+│                    #   - allow filtering list by customer, date
+│
+└── transaction      # CRUD not needed via cli, transactions will only be added via "file import"
+    ├── read         # fetch transaction details
+    │                #   - CREATE not needed, they will only be created via "file import" function
+    │                #   - UPDATE not needed, transactions are immutable
+    │                #   - DELETE not needed, transactions are immutable
+    └── list         # list transactions (with filtering)
+```
+
+## Global flags:
+--env=[dev,test]                  # production assumed
+--quiet                           # for scripts only caring about exit codes
+--help                            # display basic usage information
+--format=[raw,json,csv,columns]   # columns assumed
+
+## Implementation Notes (added during CLI expansion)
+
+The following clarifications were made while implementing the CLI stubs:
+
+- **Positional IDs**: `read`, `update`, `delete`, and `credit` subcommands that operate on a single entity take a positional `id` argument (e.g., `card read <id>`, `invoice credit <id>`).
+- **Card create**: Uses flags `--customer`, `--status`, `--description`, `--pin`.
+- **Card list**: Optional filters `--customer` and `--status`.
+- **Customer create**: Uses flags `--id` and `--name`.
+- **File export**: Takes `--format` to specify the target export format.
+- **Invoice create**: Uses flags `--batch`, `--from`, `--to`, `--customer`, and `--all`. The caller must supply either `--batch` or a `--from`/`--to` date range, and either `--customer` or `--all`.
+- **Invoice list**: Optional filters `--customer` and `--date`.
+- **Transaction list**: Optional filters `--customer`, `--card`, `--batch`, `--from`, `--to`.
+- **Global `--env`**: Accepts `dev` or `test`; omitted means production.
+- **Global `--format`**: Defaults to `columns`.