Billing and expenses

API reference for invoices and their lines, quotes, products, taxes and expenses.

These endpoints need the Sales area of the key's role, apart from expenses, which need Financial. See Keys and permissions.

Invoices

Endpoint	Does
GET `invoices/read.php`	Lists invoices, or gets one

Parameter	Does
`invoice_id`	Just this invoice
`client_id`	Just this client's invoices
`limit`, `offset`	Paging

Every invoice is listed, whatever its status. invoice_amount is its total. ITFlow works out the rest of the sums and adds them to each invoice:

Field	Notes
`invoice_subtotal`	The total before tax
`invoice_tax`	The tax
`invoice_taxes`	The tax by each part of it, as on the invoice: a `name` and an `amount`
`invoice_tax_registrations`	The tax registration lines printed on the invoice

{
  "success": "True",
  "count": 1,
  "data": [
    {
      "invoice_id": "475",
      "invoice_prefix": "INV-",
      "invoice_number": "475",
      "invoice_scope": "Wireless upgrade - two access points for the treatment rooms",
      "invoice_status": "Draft",
      "invoice_date": "2026-10-21",
      "invoice_due": "2026-11-05",
      "invoice_amount": "824.30",
      "invoice_currency_code": "USD",
      "invoice_client_id": "1",
      "invoice_subtotal": 790,
      "invoice_tax": 34.3,
      "invoice_taxes": [ { "name": "PA Sales Tax 6%", "amount": 29.4 }, { "name": "Allegheny County 1%", "amount": 4.9 } ],
      "invoice_tax_registrations": [ "Allegheny County Sales Tax No. 75520193" ]
    }
  ]
}

Fields: invoice_id, invoice_prefix, invoice_number, invoice_scope, invoice_status, invoice_date, invoice_due, invoice_discount_amount, invoice_credit_amount, invoice_amount, invoice_currency_code, invoice_note, invoice_url_key, invoice_category_id, invoice_recurring_invoice_id, invoice_quote_id, invoice_client_id, invoice_created_at, invoice_updated_at, invoice_archived_at, and the sums above.

Invoices are read only. Payments can't be read through the API.

Invoice lines

Endpoint	Does
GET `invoice_items/read.php`	An invoice's lines, or one line
POST `invoice_items/create.php`	Adds a line to an invoice

Read

Parameter	Does
`invoice_id`	This invoice's lines, in their order. You need this or `item_id`.
`item_id`	Just this line
`client_id`	Only if the invoice is this client's
`limit`, `offset`	Paging

Each line comes with its tax rate's tax_name and tax_percent.

{
  "success": "True",
  "count": 1,
  "data": [
    { "item_id": "1956", "item_name": "Ubiquiti U6-Pro Access Point", "item_description": "Wi-Fi 6 access point, ceiling mounted", "item_quantity": "2.00", "item_price": "245.00", "item_subtotal": "490.00", "item_tax": "34.30", "item_total": "524.30", "item_order": "1", "item_tax_id": "2", "item_product_id": "96", "item_invoice_id": "475", "tax_name": "Allegheny County Sales Tax", "tax_percent": "7.0000" }
  ]
}

Fields: item_id, item_name, item_description, item_quantity, item_price, item_subtotal, item_tax, item_total, item_order, item_tax_id, item_product_id, item_invoice_id, item_created_at, item_updated_at, item_archived_at, tax_name, tax_percent.

Create

Field	Notes
`invoice_id`	Required. The invoice can't be paid already.
`name`	Required, up to 200 characters
`qty`	Required, more than 0
`price`	The price of one
`description`
`tax_id`	A tax rate's `tax_id`, `0` for no tax, or `default` for the rate the client - or the product - usually has
`product_id`	The product it is. One whose stock is tracked has the quantity taken from stock, and the line is turned down if there isn't enough.
`item_order`	Where it goes among the lines
`client_id`	The invoice's client. Needed when the key's agent can see only some clients.

The invoice's totals are worked out again afterwards.

curl -X POST https://itflow.example.com/api/v1/invoice_items/create.php \
  -H "Content-Type: application/json" \
  -d '{"api_key": "YOUR_API_KEY", "invoice_id": 475, "name": "Patch cables", "description": "Cat6, 3 ft", "qty": 4, "price": 6.50, "tax_id": "default"}'

Quotes

Endpoint	Does
GET `quotes/read.php`	Lists quotes, or gets one

Parameter	Does
`quote_id`	Just this quote
`client_id`	Just this client's quotes
`limit`, `offset`	Paging

Like invoices, each quote comes with quote_subtotal, quote_tax, quote_taxes and quote_tax_registrations. On a quote with monthly lines, those are for the one-time part, and quote_monthly_amount is the monthly total.

{
  "success": "True",
  "count": 1,
  "data": [
    { "quote_id": "2", "quote_prefix": "QUO-", "quote_number": "2", "quote_scope": "Uninterruptible power supply for the comms rack", "quote_status": "Accepted", "quote_amount": "1312.95", "quote_monthly_amount": "0.00", "quote_subtotal": 1265, "quote_tax": 47.95, "quote_taxes": [ { "name": "PA Sales Tax 6%", "amount": 41.1 }, { "name": "Allegheny County 1%", "amount": 6.85 } ] }
  ]
}

Fields: quote_id, quote_prefix, quote_number, quote_scope, quote_status, quote_discount_amount, quote_date, quote_expire, quote_amount, quote_monthly_amount, quote_currency_code, quote_note, quote_url_key, quote_category_id, quote_client_id, quote_created_at, quote_updated_at, quote_archived_at, and the sums above.

Products

Endpoint	Does
GET `products/read.php`	Lists your products and services, or gets one

Parameter	Does
`product_id`	Just this product
`limit`, `offset`	Paging

Products aren't a client's, so client_id doesn't apply. The list includes archived products.

{
  "success": "True",
  "count": 1,
  "data": [
    { "product_id": "1", "product_name": "Managed Workstation", "product_type": "service", "product_code": "MS-WKS", "product_price": "65.00", "product_currency_code": "USD", "product_frequency": "month", "product_track_stock": "0", "product_tax_id": "0", "product_category_id": "15" }
  ]
}

Fields: product_id, product_name, product_type, product_description, product_notes, product_code, product_vendor_part, product_location, product_price, product_cost, product_currency_code, product_frequency, product_seat_source, product_track_stock, product_reorder_level, product_reorder_qty, product_asset_type, product_make, product_model, product_warranty_months, product_tax_id, product_category_id, product_vendor_id, product_created_at, product_updated_at, product_archived_at.

Taxes

Endpoint	Does
GET `taxes/read.php`	Lists your tax rates, or gets one

Parameter	Does
`tax_id`	Just this rate, archived or not
`archived`	`1` to include archived rates
`limit`, `offset`	Paging

{
  "success": "True",
  "count": 1,
  "data": [
    {
      "tax_id": 2,
      "tax_name": "Allegheny County Sales Tax",
      "tax_percent": 7,
      "tax_description": "Pennsylvania 6% plus the Allegheny County local 1%",
      "tax_registration_number": "75520193",
      "tax_archived_at": null,
      "tax_replaced_by": 0,
      "tax_default": false,
      "tax_components": [
        { "name": "PA Sales Tax", "percent": 6, "compound": false, "registration_number": "75520193" },
        { "name": "Allegheny County", "percent": 1, "compound": false, "registration_number": "75520193" }
      ]
    }
  ]
}

tax_percent is the whole rate, and tax_components its parts. A part that's compound is charged on top of the parts before it. tax_default is true for the rate new lines get, and tax_replaced_by is the rate that replaced a changed one. See Taxes.

Expenses

Endpoint	Does
GET `expenses/read.php`	Lists expenses, or gets one

Parameter	Does
`expense_id`	Just this expense
`client_id`	Just this client's expenses. `0` for those that aren't a client's.
`limit`, `offset`	Paging

{
  "success": "True",
  "count": 1,
  "data": [
    { "expense_id": "13", "expense_description": "Hardware supplied to Ravenwood Dental Group", "expense_amount": "1762.00", "expense_date": "2026-10-14", "expense_vendor_id": "1", "expense_category_id": "76", "expense_client_id": "1", "expense_billable": "1", "expense_invoice_id": null }
  ]
}

Fields: expense_id, expense_description, expense_amount, expense_tax_id, expense_tax_amount, expense_currency_code, expense_date, expense_reference, expense_payment_method, expense_receipt, expense_vendor_id, expense_client_id, expense_category_id, expense_account_id, expense_refund_of_id, expense_recurring_expense_id, expense_billable, expense_markup, expense_invoice_id, expense_invoice_item_id, expense_import_key, expense_paid_by, expense_reimbursement_id, expense_reconciliation_id, expense_created_by, expense_created_at, expense_updated_at, expense_archived_at.