> For the complete documentation index, see [llms.txt](https://api-docs.flagstoneim.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://api-docs.flagstoneim.com/readme.md).

# Flagstone API Documents

We're the UK leader in savings API integration.

We connect pension providers, wealth managers, and financial institutions to 60+ banks through one integration.

Our APIs have powered our multi-billion pounds savings platform since 2019.

Partners use them every day to open accounts, receive interest, and report client balances in a regulated UK context.

|                                                              |                                                 |
| ------------------------------------------------------------ | ----------------------------------------------- |
| **In production since**                                      | 2019                                            |
| **Instructions processed annually**                          | 100 million+                                    |
| **Capital transferred to date**                              | £100 billion+                                   |
| **Partner bank network**                                     | 60+ banking institutions                        |
| **Sustained throughput**                                     | Up to 50 requests/second                        |
| **Processing window**                                        | 24-hour instruction cycle                       |
| **Regulatory status**                                        | FCA authorised and regulated                    |
| **Client coverage**                                          | Individual, Company                             |
| **FSCS (Financial Services Compensation Scheme) protection** | Per-product, per-institution visibility via API |

Whether you run a large pension scheme or a SIPP (Self-Invested Personal Pension) proposition, the pattern is simple.

You integrate once with a mature, version-stable API suite and scale with confidence.

***

## 🔗 Core Integration Flow

<figure><img src="/files/H2ZbO6pF1IrIUk6yNih9" alt="Core integration flow"><figcaption></figcaption></figure>

1. **Register your client** - Individual or company, via the Client API
2. **Browse available products** - Fixed term, instant access, and notice accounts via the Product Catalog API
3. **Submit instructions** - Deposits, withdrawals, and other operations via the Instruction Request API
4. **Track positions** - View deposit accounts, interest, and pending payments via the Portfolios API

***

## 📚 API Suite

| API                                                      | What it does                                         | Version      |
| -------------------------------------------------------- | ---------------------------------------------------- | ------------ |
| [Client API](/apis/clients.md)                           | Onboard and manage individual & company clients      | `2020-08-01` |
| [Product Catalog API](/apis/products.md)                 | Browse savings products, rates, and terms            | `2022-07-01` |
| [Instruction Request API](/apis/instruction-requests.md) | Submit deposits, withdrawals, and other instructions | `2021-11-01` |
| [Portfolios API](/apis/portfolios.md)                    | View client portfolios and deposit account positions | `2020-04-01` |
| [Instruction Batches API](/apis/instruction-batches.md)  | View and manage daily instruction settlement batches | -            |

Each API has a dedicated guide with business context, endpoint reference, and request/response examples. Full OpenAPI 3.0 specifications are available for each:

* [Client API Reference](/api-reference/client-api-ref.md)
* [Products API Reference](/api-reference/products-api-ref.md)
* [Instruction Request API Reference](/api-reference/instruction-request-api-ref.md)
* [Portfolios API Reference](/api-reference/financial-partners-api-ref.md)
* [Instruction Batches API Reference](/api-reference/instruction-batches-api-ref.md)

***

## 🏗️ Platform Architecture

| Capability              | Detail                                          |
| ----------------------- | ----------------------------------------------- |
| **Authentication**      | API key via `cdpapi-Subscription-Key` header    |
| **Environments**        | Sandbox and Production                          |
| **Specification**       | OpenAPI 3.0.1 for all APIs                      |
| **Client types**        | Individual and Company                          |
| **Currencies**          | GBP, EUR, USD                                   |
| **Product types**       | Fixed Term, Instant Access, Notice              |
| **FSCS protection**     | Visibility per product and institution          |
| **Concurrency control** | Optimistic versioning on clients and portfolios |
| **Idempotency**         | Built-in                                        |

***

## 🚀 Quick Start

1. [Get your API credentials](/getting-started.md) - sandbox and production keys
2. [Understand the data model](/core-concepts.md) - how clients, products, instructions, and portfolios relate
3. [Create your first client](/apis/clients.md) - start with the Client API
4. [Submit your first deposit](/apis/instruction-requests.md) - place an instruction against a product