## Prerequisites
Before you create an invoice, you will need some information handy.
### Get your Organization ID and API Key
Log into the app and go to your [API Keys page](🔗). There you will find your organization ID and API keys.
### Create or get your Counterparty
Before you can create an invoice, you need to have a counterparty in Modern Treasury.
You can get an existing counterparty's ID from your counterparties page [here](🔗). If you do not have the counterparty in Modern Treasury, you can create a counterparty either via the web app or the API.
Here is an example API request to create a counterparty:
Once the counterparty is successfully created, save the counterparty ID from the response body, which in this case is `342b0006-97b9-4b59-bd3d-5dfb220ff18b`:
For more details, see our [API reference for counterparties](🔗).
### Get your Originating Account ID
When you send a counterparty an invoice, you must designate one of your [internal accounts](🔗) as the account that money will deposited into when the invoice is paid. If the invoice is paid via ACH debit, then the internal account will originate an ACH debit against the counterparty's bank account.
To get an internal account ID, you can pick one from your accounts page [here](🔗).
## Create an Invoice
Next, you will create an invoice using our API. You must include the following fields:
Invoice counterparty ID
Originating account ID
Due date
You can only set the invoice's [contact details](🔗) (your email, phone number, and website) when creating the invoice; you will not be able to update these. When creating an invoice, you are able to create [invoice line items](🔗) in the same request.
If you set `auto_advance` to true, the invoice will automatically be marked as ready-to-collect and will automatically progress the invoice to the status `unpaid`. An invoice in the `unpaid` status cannot be modified afterwards.
If you set `payment_method` to automatic, the `receiving_account_id`, `payment_effective_date`, and `payment_type` fields must be set.
See our invoice [API reference docs](🔗) for more invoice fields that you can set.
The response will look like the following:
You can view the invoice at the hosted URL in the response body.
#### **(_Optional_) Adding your company logo to invoices**
The invoice will include your company logo automatically. To change or add a logo for your organization, navigate to your organization's [settings](🔗) page and click the **Logo** tab.
## Update a Draft Invoice
If you want to update the invoice's details, you can do so through the API:
To see the complete list of invoice fields you can update, visit our [API reference docs](🔗).
### Add additional line items to an invoice
When adding invoice line items to an existing invoice, you can use the invoice ID to add additional line items. Each line item requires a separate API request.
See our API reference for invoice line items [here](🔗).
## Share an Invoice with a Counterparty
To mark the invoice as ready-to-collect, update the invoice, indicating if you want to include the embedded payment UI and updating the invoice status to `unpaid`.
Now, the invoice is ready-to-collect and you can send the invoice's counterparty the hosted URL.