---
title: "Creates a new fixed-amount billing entry against a task."
method: POST
path: "/api/FixedAmount"
tags: ["FixedAmount"]
---

# Creates a new fixed-amount billing entry against a task.

`POST /api/FixedAmount`

The project is always derived from the task, and the amount is in the currency of the customer the task's project belongs to. Fixed amounts cannot be added to tasks on internal or archived projects. The created record is immediately visible to GET /api/FixedAmount and invoiceable through the invoicing endpoints.

## Request body

- NewFixedAmount — Payload for creating a new fixed-amount billing entry against a task.
  - `TaskIDFK` integer — The task the fixed amount is added to. Required. Must exist in the authenticated account; the project is always derived from the task. Multiple fixed amounts per task are allowed.
  - `Amount` number, double — The fixed billing amount, in the currency of the customer the task's project belongs to. Required. Rounded to that currency's decimal places.
  - `InventoryItemIDFK` integer — The inventory item used when this fixed amount is invoiced. Required; there is no default.
  - `Notes` string — Plain text notes, maximum 255 characters.

## Response `200`

Returns the created fixed-amount entry.

- FixedAmountDetails — A fixed-amount billing entry for fixed-price project invoicing, linked to a project, task, and inventory item.
  - `FixedAmountID` integer — Unique identifier for the fixed amount entry.
  - `ProjectIDFK` integer — The project this fixed amount is linked to.
  - `ProjectTitle` string — Title of the associated project.
  - `ProjectCode` string — Short code of the associated project.
  - `TaskIDFK` integer — The task this fixed amount is linked to, if any.
  - `TaskTitle` string — Title of the associated task.
  - `InventoryItemIDFK` integer — The inventory item used for this fixed amount.
  - `InventoryItemName` string — Name of the inventory item.
  - `Amount` number, double — The fixed billing amount.
  - `Notes` string — Additional notes on the fixed amount.
  - `isInvoiced` boolean — Whether this fixed amount has been included on an invoice.
  - `CustomerIDFK` integer — ID of the customer company the fixed amount's project belongs to.
  - `InvoiceLineItemIDFK` integer — The invoice line item this fixed amount is linked to, if it has been invoiced.
  - `InvoiceIDFK` integer — The invoice (Transaction) the linked line item belongs to. Only populated when includeInvoiceDetails=true.
  - `DateCreated` string, date-time — Date the record was created.
  - `DateUpdated` string, date-time — Date the record was last updated.
  - `UpdatedByUserIDFK` integer — User ID of the last person to update this record.

## Other responses

- `401` — Unauthorized

## Changes

- **2026-08-30** `e99843f3c878` — 1 info
  - endpoint added

[Change history](https://skmtc.dev/avaza/apis/avaza-api-documentation/changes/api/FixedAmount/post.md)

---

[API](https://skmtc.dev/avaza/apis/avaza-api-documentation.md) · [All operations](https://skmtc.dev/avaza/apis/avaza-api-documentation/llms.txt) · [OpenAPI document](https://skmtc-service-production.skmtc.workers.dev/v1/apis/avaza/avaza-api-documentation/revisions/e99843f3c878/schema)