Create interim payment

Creates a new interim payment (partial payment, advance payment, prepayment) in the specified project.

How it works:

• The new payment is added to the project with the provided title, description, and amount
• Sort order is automatically set to the maximum existing sort order plus 1 (appears at the end of the list)
• The payment is initially marked as not billed (isBilled: false)
• Description can be provided as HTML or Markdown and is automatically converted to internal IDoc format

Required fields:

• title: Short label for the payment (e.g., “Prepayment”, “50% Deposit”, “Milestone 1”)
• amount: Payment amount (must be positive, minimum 0.01)

Optional fields:

• description: Detailed notes about the payment (e.g., “Client paid €1,000 upfront”). Can be provided as HTML or Markdown format

What happens after creation:

• The payment becomes available for billing in the invoicing system
• When used in an invoice, it is automatically deducted from the final invoice amount
• The payment can be reordered using the sort endpoint

Validation:

• Amount must be a positive number (minimum 0.01)
• Title cannot be empty
• Project must exist and be accessible

Permissions: Requires Projects.edit permission

curl -X POST "https://leadtime.app/api/public/projects/string/interim-payments" \
  -H "Authorization: Bearer YOUR_ACCESS_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
  "amount": 10000,
  "description": "<p>Payment for Q1 milestone - Client paid €1,000 upfront</p>",
  "title": "Advance Payment Q1"
}'

const response = await fetch("https://leadtime.app/api/public/projects/string/interim-payments", {
  method: "POST",
  headers: {
    "Authorization": "Bearer YOUR_ACCESS_TOKEN",
    "Content-Type": "application/json"
  },
  body: JSON.stringify({
  "amount": 10000,
  "description": "<p>Payment for Q1 milestone - Client paid €1,000 upfront</p>",
  "title": "Advance Payment Q1"
})
});

import requests

response = requests.post(
    "https://leadtime.app/api/public/projects/string/interim-payments",
    headers={
        "Authorization": "Bearer YOUR_ACCESS_TOKEN",
        "Content-Type": "application/json"
    },
    json={
  "amount": 10000,
  "description": "<p>Payment for Q1 milestone - Client paid €1,000 upfront</p>",
  "title": "Advance Payment Q1"
},
)

{
  "success": true
}