How to connect Fathom to Claude: what accounting firms are building

No native integration exists between Fathom and Claude. Fathom produces visual financial reports, KPI dashboards, and benchmarking analysis, but it does not connect to external AI models for narrative generation. Formulaic builds the pipeline between your Fathom reporting data and Claude’s API, producing advisory commentary, board-ready narrative summaries, trend analysis, and client meeting preparation that turns Fathom’s visual output into complete advisory deliverables. This applies to accounting practices using Fathom for financial reporting who want to add an AI-powered narrative layer on top.

Short answer: No native integration exists between Fathom and Claude. Formulaic builds custom pipelines that extract Fathom’s financial analysis data and route it to Claude for advisory commentary, board-ready summaries, and client meeting preparation.

What this integration does

Fathom answers the question “what happened?” with charts, KPIs, and visual analysis. Claude answers the question “what does it mean and what should we do about it?” with written narrative. Together, they produce the complete advisory deliverable that clients pay for.

Advisory commentary generation. Fathom shows that gross margin dropped from 42% to 37% over three months. Claude writes the paragraph explaining that margin compression coincided with the raw material cost increase in Q2, that the client absorbed the increase rather than passing it to customers, and that maintaining current pricing will reduce annual profit by approximately £85,000. The accountant reviews and adjusts the commentary. The insight is Fathom’s. The articulation is Claude’s.

Board-ready summaries. Clients with boards or investors need written summaries, not just dashboards. The pipeline takes Fathom’s complete analysis (P&L trends, balance sheet health, KPIs, cash flow forecast) and produces a structured board summary: executive overview, financial highlights, areas requiring attention, and recommended actions. This follows a consistent format that the board expects each period.

Trend identification. Claude processes multiple periods of Fathom data and identifies patterns that are difficult to spot on individual monthly reports: gradual shifts in cost ratios, seasonal patterns across years, correlations between operational KPIs and financial outcomes, and leading indicators that predict cash flow problems 2-3 months in advance. These insights are flagged for the accountant to validate and communicate to the client.

Client meeting preparation. Before a client advisory meeting, the pipeline generates a structured agenda from Fathom data: performance highlights to celebrate, concerns to raise, questions to ask the client, and advisory recommendations to present. The partner walks into the meeting prepared with specific talking points rather than generic financial review topics.

How the data flows

Fathom’s data is already processed financial analysis, making this one of the cleaner pipeline integrations.

Extraction from Fathom. Formulaic connects to Fathom’s API to pull: KPI values and trends, P&L analysis by period, balance sheet metrics, cash flow summaries, budget variances, and any custom metrics the practice has configured. For practices using Fathom’s benchmarking features, comparative data is also extracted.

Enrichment. For deeper analysis, the pipeline can also pull underlying data from Xero or Sage (Fathom’s data sources). This provides transaction-level detail when Claude needs to explain why a specific KPI changed. Fathom shows the margin dropped. The Xero data shows which cost categories drove the increase.

Processing. Fathom’s analysis data feeds into structured prompts: the financial metrics, period-over-period trends, budget variances, a task instruction (generate commentary, identify trends, prepare agenda), your practice’s advisory style and terminology, and the client’s business context. Claude returns narrative paragraphs, structured agendas, or flagged insights depending on the workflow.

Delivery. Advisory commentary exports as Word documents that complement Fathom’s visual reports. Board summaries output as formatted documents following the client’s board pack template. Meeting agendas email to the partner before the scheduled meeting. Trend alerts post to the practice’s internal system for review.

Every report generation is logged: which client’s data was processed, what Fathom metrics were included, what narrative was produced, and who reviewed it.

Use cases we build

Monthly advisory packs for premium clients. A practice offers monthly advisory services to 20 clients at £500-£1,500/month. Each month requires a written pack alongside the Fathom visual report. The pipeline generates the narrative sections: performance summary, KPI commentary, cash flow analysis, and recommended actions. Partners previously spent 45-60 minutes per pack writing commentary. With the pipeline, they spend 10-15 minutes reviewing and personalising. Across 20 clients, this recovers 12-16 hours monthly, which either reduces costs or allows the practice to take on more advisory clients without adding headcount.

Board reporting for corporate clients. A mid-market accounting practice prepares quarterly board packs for 8 corporate clients. Each pack requires: executive summary (one page), financial performance narrative (two pages), KPI analysis with commentary, and forward-looking outlook. The pipeline generates all narrative sections from Fathom data. Board members receive professional, consistent reporting. The practice delivers board packs that previously required partner-level writing time.

Benchmarking commentary. For clients in similar industries, Fathom provides benchmarking data. Claude generates comparative commentary: how the client performs against the benchmark on key metrics, where they lead, where they lag, and what the top performers in the benchmark do differently. This turns Fathom’s benchmark charts into actionable advisory content.

Annual strategy meeting preparation. Before an annual strategy meeting with a client, the pipeline analyses 12 months of Fathom data and produces: a year-in-review narrative, key achievements and challenges, trend analysis, strategic risks identified from the data, and suggested priorities for the coming year. The partner arrives at the strategy meeting with a substantive discussion document rather than a slide deck of charts.

What about using GPT or Copilot instead?

GPT (via OpenAI) handles the same workflows. It processes Fathom data and generates narrative effectively. Claude tends to produce more consistent formatting and follows detailed advisory style instructions more precisely, which matters when every client pack needs to match the practice’s quality standards.

Microsoft Copilot can work with Fathom data exported to Excel or PowerPoint, but it doesn’t connect to Fathom directly. The accountant exports, formats, and asks Copilot to help. This is better than nothing but still manual.

The Formulaic pipeline automates the entire flow: Fathom data extraction, narrative generation, formatting, and delivery. No exports, no manual steps, no inconsistency between client packs.

For practices where advisory services are a growth priority, the quality and consistency of the narrative output directly affects client retention and willingness to pay advisory-level fees. A pipeline that produces professional advisory commentary at scale is a revenue enabler, not just a time saver.

Timeline and investment

Every build is scoped and priced based on complexity. Simpler data syncs take less time than multi-system orchestration with compliance requirements. Start with an audit to get a clear proposal.

Take the AI Opportunity Scorecard to see which integrations would deliver the highest ROI for your firm.