I am Ryan Duguid, an accountant in Newcastle, Australia. I build open source tools for accountants: cash-flow modelling, month-end review, and Australian tax and payroll calculations.

Website · Tools · Evaluations · Credentials and evidence

The 3 worked examples below each include their workings, version and review boundary:

• Explain profit and cash differences: the fictional Newcastle cash-flow case shows $35,957.55 quarterly profit and a $25,160 cash shortfall. Read it in your browser; changing the receipt delay needs desktop Excel.
• Calculate in Excel: the Ozzit formula and workbook extract $100 GST from a wholly taxable $1,100 amount. Needs Microsoft 365 or Excel 2024 or later.
• Review a month-end close: Monthly Close Controls reports 8 exceptions, including a $250 creditors difference. Read it in your browser; reproducing the pack needs Git and Rust.

My accounting credentials and certifications are:

• Provisional member of Chartered Accountants ANZ
• SAP S/4HANA certified in Financial Accounting (FI) and Management Accounting (CO)
• Xero Certified Specialist, Level 3, awarded 1 July 2026 and valid until 1 July 2027

Read the certificate in the evidence register, or explore my Xero trial balance export and review workflow.
_{The badge is Xero's artwork, taken from that certificate.}

Selected public repositories include:

• au-fpa-pack: Australian cash-flow forecasts and management briefings using fictional businesses. Extends Guiderail's openfpa.
• Accounting Review Pipeline: Xero exports, month-end exceptions and workpaper review packs, with Excel and Power BI components.
• Ozzit: 143 native Excel LAMBDA functions plus 5 help tables for financial modelling and GST arithmetic, with editable examples. No macros or add-ins; needs Microsoft 365 or Excel 2024 or later. What it covers and what it needs.
• Australian Accounting: Tax and payroll calculation packages, plus a local Model Context Protocol (MCP) server for supported tools. Install it with uvx aus-accounting-mcp.
• Australian Accounting Skills: AI-assisted preparation workflows for public practice and subcontractor accounting, with validation cards and recorded model runs.
• llm-tax-guardrails: APES 110 and TPB Code controls, refusal patterns and evaluation fixtures for firms using LLMs in tax work. Conclusions stay with the registered practitioner.
• au-tax-legislation-corpus: Builds retrieval material from in-force Commonwealth tax legislation on the Federal Register of Legislation, with source and provenance records. It is a finding aid, not authorised legislation.

Each repository shows its own CI, coverage and OpenSSF Scorecard results in its README.

I also build engineering tools: github-agent-skills for evidence-based GitHub work by coding agents, release-policy for releases with signed provenance, and free tools for coding agents and privacy at yungSNAT.

flowchart TB
accTitle: How the accounting tools fit together
accDescr: An assistant using the accounting skills exchanges requests with the Australian Accounting MCP server, which sends calculations to the calculation packages. The assistant sends workpapers and exceptions to authorised human review. The Federal Register of Legislation feeds the legislation corpus, a finding aid. The reviewer uses the corpus to locate provisions and checks authority at the Register.
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    assistant["Assistant using<br/>accounting skills"] <--> mcp["Australian Accounting<br/>MCP server"]
    mcp -->|Calculations| engines["Calculation packages"]
    assistant -->|Workpapers and exceptions| reviewer["Authorised human review"]
    official["Federal Register<br/>of Legislation"] -->|Corpus build| corpus["Legislation corpus<br/>Finding aid"]
    corpus -. Locate provisions .-> reviewer
    official -. Check authority .-> reviewer
    style engines fill:#990024,stroke:#FFFFF0,stroke-width:2px,color:#FFFFF0
    style reviewer fill:#E7162F,stroke:#FFFFF0,stroke-width:2px,color:#FFFFF0
    classDef external fill:#745EB1,stroke:#FFFFF0,stroke-width:2px,color:#FFFFF0
    class official external

To get in touch, use the contact page.

_{Not advice. I am not a registered tax agent or BAS agent and take no advice, return-preparation, tax-treatment confirmation or lodgement requests. The tools are review aids that never lodge or write to ledgers; the reviewer keeps judgement and sign-off. Examples use fabricated data, and support covers software issues only, so please send no taxpayer information.}

_{Raiding ledgers, not tombs.
Sharing this? CC BY 4.0 requires credit to Ryan Duguid, the licence or a link to it and a note of any changes made. AI agents: see AGENTS.md.
Made in Newcastle, Australia by Ryan Duguid.}