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.

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🔗 Core Integration Flow

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

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📚 API Suite

API	What it does	Version
Client API	Onboard and manage individual & company clients	2020-08-01
Product Catalog API	Browse savings products, rates, and terms	2022-07-01
Instruction Request API	Submit deposits, withdrawals, and other instructions	2021-11-01
Portfolios API	View client portfolios and deposit account positions	2020-04-01
Instruction Batches API	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

• Products API Reference

• Instruction Request API Reference

• Portfolios API Reference

• Instruction Batches API Reference

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🏗️ 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

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🚀 Quick Start

1. Get your API credentials - sandbox and production keys

2. Understand the data model - how clients, products, instructions, and portfolios relate

3. Create your first client - start with the Client API

4. Submit your first deposit - place an instruction against a product