From Excel to AI Agents: A Practical Framework for Automating Finance Processes
Accountex/FD Show - May 2026
Over the last twenty years I’ve held six roles across Deloitte, KPMG, HSBC, Barclays and Avanade – and the question I keep coming back to is which one AI is reshaping the most. The answer is all of them: every role came down to messy data, a few rules, some judgement, and something people can trust and act on. This session shows that through Excel – a custom agent skill in Claude in Excel that runs like a VBA macro, written in plain English instead of code.
What you'll see
01. The Showdown: Me vs AI
Live in Excel — a four-entity reconciliation and a 3-statement financial model. First the “manual” way with Excel templates and Copilot (including Copilot for Finance!), then with Claude in Excel. A plan-first prompt for the reconciliation, and a built-in 3-statement-model skill for the accounts. Minutes later: every account reconciled, variances explained, a fully connected Income Statement, Balance Sheet and Cashflow Statement in Excel built from the reconciled ledger.
02. Powerful, but is it enough?
This is undoubtedly brilliant for one-off personal productivity, but a business process must be repeatable, standardised and auditable. Gen AI is by nature probabilistic: it can answer differently next time, and a single prompt can’t carry everything it needs to know. This creates scope creep – the agent races ahead and drifts.
03. Determinism through context, not prompts
The fix isn’t a longer prompt – it’s context engineering. Agent Skills are curated markdown (text) files that teach an agent to do a task the same way every time. A create-implementation-plan skill forces a plan of discrete, atomic steps before any action, so the process is consistent and auditable.
04. Packaging skills into deployable enterprise architecture
One custom skill is a step towards a system. Treat agents like a team of people: job roles (instructions) + skills + tools (MCP) + data & context. Agent = Model + Harness. That’s how finance processes get automated for real.
First watch the full session (48 minutes)..
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...Now build your own custom skill in Excel
In the session you watched a fiddly salary-accruals process — prepayments and accruals for fixed-term contractors — turned into a reusable custom skill. Now do it yourself. You’ll need Claude Desktop with the Excel add-in and the files which you can download below
Grab a "utility skill" from the Internet
Search github / awesome-copilot → skills folder → create-implementation-plan → SKILL.md → Download raw file. Compress it to a ZIP named create-implementation-plan.zip.
Install it in Claude
Claude Desktop → your profile → Settings → Capabilities → Skills have moved to… Customize → + → Create skill → Upload a skill → choose your ZIP.
Walk the workbook
Open the Simple Salary Accrual Journal. Tour the tabs: General Ledger (fixed amounts booked by the ERP), Bank Statement (what was actually paid), Staff List (name ↔ role, cost centre & company code), Calcs (SUMIFS differences) and Journal (accrual / prepayment lines where debits = credits).
Generate a plan with Claude in Excel
Home ribbon → Claude → open the side pane. Add the process-script file, then prompt: “Attached is a process script for creating a calcs and journal sheet… create an implementation plan to build these from the input sheets, using the /create-implementation-plan skill.” Then refine: “keep it dynamic for any number of employees and months.”
Build & Verify
Prompt: “Create the new calcs and journals sheets based on this implementation plan in this workbook.” Approve changes with Allow once. Check the numbers match the original and that total debits = total credits.
Turn it into a reusable skill
Prompt: “Use this plan to create a custom skill called create-salary-accruals.” Save it to Claude. Now open a different month’s workbook and run /create-salary-accruals — it adapts to new employees, cost centres and periods automatically. That’s a finance process automated.
Interactive Tutorial: Build your own Excel Agent
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