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

POST/projects/{projectId}/interim-payments

Authorization

AuthorizationOAuth2 access token · headerrequired

Scopes:api:write

AuthorizationBearer token (JWT) · headerrequired

Path parameters

projectIdstringrequired

Request body

requiredapplication/json

amountnumberrequired

Payment amount in the workspace currency. Must be a positive number with a minimum value of 0.01. This amount will be deducted from the final invoice when the payment is billed.

descriptionstring

Optional detailed description or notes about the payment. Can be provided as HTML (e.g., "<p>Client paid €1,000 upfront</p>") or Markdown format. The system automatically detects the format and converts it to internal IDoc format for storage. If not provided, the description will be empty.

titlestringrequired

Short label or title for the payment. Examples: "Prepayment", "50% Deposit", "Milestone 1", "Advance Payment Q1". This field is required and cannot be empty.

Responses

201

Interim payment created successfully

successbooleanrequired

Operation success flag

400

Invalid input data

401

Unauthorized - Invalid or missing authentication token

403

Forbidden - Insufficient API scopes or permissions

404

Project not found

Try it

Server

Base URLCustom base URLOverrides the selected server when set.

Authorization

OAuth2 access tokenRemember on this deviceInclude my values in samples

Parameters

projectIdpath*

Bodyapplication/json

amountnumber*Payment amount in the workspace currency. Must be a positive number with a minimum value of 0.01. This amount will be deducted from the final invoice when the payment is billed.descriptionstringOptional detailed description or notes about the payment. Can be provided as HTML (e.g., "<p>Client paid €1,000 upfront</p>") or Markdown format. The system automatically detects the format and converts it to internal IDoc format for storage. If not provided, the description will be empty.titlestring*Short label or title for the payment. Examples: "Prepayment", "50% Deposit", "Milestone 1", "Advance Payment Q1". This field is required and cannot be empty.

Request

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: "{\n  \"amount\": 10000,\n  \"description\": \"<p>Payment for Q1 milestone - Client paid €1,000 upfront</p>\",\n  \"title\": \"Advance Payment Q1\"\n}"
});

import requests

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

Response

{
  "success": true
}