MCP · works in ChatGPT, Claude & Codex

File your taxes from your chat.

Add the ac-co MCP server to ChatGPT, Claude or Codex. Ask in plain English — "file our Q4 VAT return" — and ac-co prepares it, then renders a real, interactive filing app right inside the conversation. You review the numbers and tap file. It goes straight to HMRC.

See the MCP app

One-line install · read-only by default · human-in-the-loop

WORKS INChatGPTClaudeCodexCursorAny MCP client

✦

ChatGPT

via ac-co MCP

connected

Can you file our Q4 VAT return?

✦

On it — I'll pull the figures from your books and prepare the return with ac-co.

⚙ac-co · prepare_vat_returncalled

{ period: "2025-Q4", entity: "Brightwell Trades Ltd" }

✦

Reconciled 1,486 entries and applied the CIS reverse charge. Here's the return — review and file when you're ready:

ac-coMCP UI

secure

VAT return · Q ending 31 Mar 2026

Brightwell Trades Ltd

VAT on sales (Box 1)£38,420

VAT reclaimed (Box 4)£14,860

Net VAT due (Box 5)£23,560

Period6 Jan – 31 Mar 2026

Ask ac-co to file something…↑

Live in ChatGPT

Wired into

ChatGPT · MCPClaude · MCPCodex · MCPCursor · MCPMCP · open protocolHMRC · recognisedOpen Banking · read-only

assistants supported today

ChatGPT · Claude · Codex — more via MCP

filings, one sentence each

VAT · SA100 · CT600 · ITSA · payroll

line to install the server

one command, or one click

of filing stays human-approved

the assistant drafts, you submit

HOW IT WORKS

From connected to filed, in four moves.

Install

Add the ac-co MCP server to ChatGPT, Claude or Codex — one command, or one click from the directory.

Connect

Authorise ac-co once. Your bank, books and HMRC links live in ac-co; the assistant only sees what you allow.

Ask

Ask in plain English — "file my VAT return", "how much CT do we owe?", "run March payroll".

File

ac-co renders an interactive app in the chat. Review the figures, tap file — it goes straight to HMRC.

SEE IT IN THE CHAT

One sentence in, a filed return out — without leaving the conversation.

Watch the assistant call ac-co, render the return as an interactive app, and file it to HMRC — in ChatGPT, Claude or Codex. Switch assistants and replay as often as you like.

ChatGPTClaudeCodex

MCP TOOLS

Real tool calls, not copy-paste prompts.

ac-co exposes typed MCP tools — prepare a return, fetch a computation, run a pay period — that the assistant calls directly. Every call is logged, scoped and reversible. No pasting figures between windows.

Typed toolsprepare_vat_return, get_ct_computation, run_payroll and more — each with a clear schema.
Every call loggedA full audit trail of what the assistant asked for and what ac-co returned.
Scoped & reversibleTools are read-only until you grant a filing scope; nothing submits without your tap.
Same engineThe exact computations behind ac-co.vat, .self-assessment and the rest — surfaced over MCP.

MCP tool call

→ ac-co.prepare_vat_return(

period: "2025-Q4",

entity: "Brightwell Trades Ltd"

)

← 200 · return prepared

net_vat_due: 23560,

status: "ready_to_file"

Logged to your audit trail · read-only scope

MCP UI

An interactive app, inside the chat .

ac-co doesn't dump a wall of text — it renders an actual filing app in the conversation. The full return, the boxes, the tax due, and a real "File to HMRC" button. Review and submit without ever leaving the chat.

Rendered in-chatA proper interactive card via MCP UI — buttons, figures and status, not just a transcript.
Review before filingExpand the boxes, check the sources, change a figure — then file when you're happy.
One tap to HMRCThe submit button files through the same recognised pipeline as the web app.
Receipt in the threadThe HMRC reference and receipt land back in the conversation and your ac-co vault.

✳

Claude

via ac-co MCP

connected

Can you file our Q4 VAT return?

✳

On it — I'll pull the figures from your books and prepare the return with ac-co.

⚙ac-co · prepare_vat_returncalled

{ period: "2025-Q4", entity: "Brightwell Trades Ltd" }

✳

Reconciled 1,486 entries and applied the CIS reverse charge. Here's the return — review and file when you're ready:

ac-coMCP UI

secure

VAT return · Q ending 31 Mar 2026

Brightwell Trades Ltd

VAT on sales (Box 1)£38,420

VAT reclaimed (Box 4)£14,860

Net VAT due (Box 5)£23,560

Period6 Jan – 31 Mar 2026

Ask ac-co to file something…↑

PERMISSIONS & SECURITY

The assistant drafts. You hold the keys .

Connections to your bank and HMRC stay inside ac-co, behind OAuth. The assistant never sees your credentials, can't move money, and can't file anything without an explicit, human tap. Read-only by default.

No credentials sharedThe model never touches your bank or HMRC logins — only ac-co's scoped tokens.
Read-only by defaultFiling needs a separate, time-boxed scope that you grant per action.
Human-in-the-loopNothing reaches HMRC without your explicit confirmation in the app.
UK data residencyYour data stays in the UK, encrypted, with the same controls as the web app.

ac-co wants permission to…

✓Read VAT figures from your books

✓Read your HMRC obligations

✓Prepare & preview returns

—File to HMRCneeds your tap

—Move moneynever

PRICING

Free to file — upgrade only for teams.

Bundled free with every ac-co product. Team and platform plans billed per seat.

Included

With any ac-co filing

£0/ extra

The MCP server is bundled with every ac-co product. Use it from any MCP client at no extra cost.

Install the server

✓ChatGPT, Claude & Codex
✓All filing tools over MCP
✓Interactive MCP UI app
✓Human-in-the-loop filing
✓Full audit trail

Teams

Shared org & roles

Most picked

£6/ seat / month

For practices and finance teams — shared connections, per-seat scopes and an org-wide audit log.

Start a team

✓Everything in Included, plus:
✓Shared client connections
✓Per-seat filing scopes
✓Org-wide audit log
✓SSO / SCIM
✓Priority support

Platform

Embed ac-co

Custom

Embed the ac-co MCP tools and UI in your own assistant or product, white-labelled.

Talk to us

✓White-label MCP server
✓Custom tool scopes
✓Branded MCP UI
✓Usage-based billing
✓Solutions engineering

TRUST

We file in your name, so we hold ourselves to the highest bar.

ac-co is HMRC-recognised software submitting through the official API. Connections to your bank and books are read-only. Every figure traces to a source, and every receipt is stored for six years.

Security paper →How we use your data →

MCP

open protocol

HMRC

recognised software

OAuth 2.1

scoped tokens

Read-only

default access

Human-in-loop

you tap to file

UK GDPR

data resident in London

FAQ

Questions people actually ask.

The Model Context Protocol is an open standard that lets AI assistants call external tools and render interactive apps. ac-co publishes an MCP server, so any MCP-capable assistant — ChatGPT, Claude, Codex and others — can prepare and file your returns through the same recognised pipeline as the web app.

No — and that's by design. The assistant can prepare and explain a return, but filing requires an explicit, human tap in the interactive app. ac-co's tools are read-only until you grant a separate, time-boxed filing scope per action.

Never. Your connections live inside ac-co behind OAuth. The assistant only ever uses ac-co's scoped tokens — it can't see your credentials and can't move money.

ChatGPT, Claude and Codex are supported now, plus other MCP clients like Cursor. Because it's the open protocol, support grows as more assistants adopt MCP.

Prepare and file VAT, Self Assessment, Corporation Tax, MTD income-tax updates and payroll; pull a tax computation; check what you owe; or explain any figure on a return. The same engine as the rest of ac-co, over MCP.

One line in your assistant's MCP settings, or one click from the directory. Then authorise ac-co once and you're ready. See install below.

INSTALL THE MCP SERVER

Bring filing into your chat.

Works in ChatGPT, Claude & Codex · read-only by default · bundled free with ac-co.

One-line install · bundled free with every ac-co product