How to Use Claude Code for BAS & GST in Australia

Claude Code is powerful, but out of the box it doesn't know Australian tax specifics — current GST rates, BAS reporting periods, PAYG brackets, or ATO lodgement requirements.

This guide shows you how to add Australian tax skills so Claude Code becomes your BAS assistant.

What You'll Get

After setup, Claude Code will be able to:

Calculate GST on invoices (10% rate, GST-free items)
Determine BAS reporting periods (monthly vs quarterly)
Calculate PAYG withholding from current tax tables
Identify deductible expenses for your industry
Explain ATO lodgement deadlines

Step 1: Install Claude Code

If you haven't already:

npm install -g @anthropic-ai/claude-code

Then authenticate:

claude auth login

Step 2: Add the BAS Skill

In your project directory, run:

npx skills-au add ato-bas-expert -a claude

This creates a .claude/skills/ato-bas-expert/ folder with the skill files.

Step 3: Reference in CLAUDE.md

Add a reference to your project's CLAUDE.md:

# Project: My Business ## Skills - .claude/skills/ato-bas-expert/SKILL.md ## Context This is an Australian business. Use Australian tax rules.

Step 4: Test It

Start Claude Code and try these prompts:

> "Calculate GST on a $1,100 invoice"

→ GST: $100, Net: $1,000

> "When is my Q3 BAS due?"

→ For July-Sept quarter: 28 October (or 25 Nov if lodging electronically through a tax agent)

> "PAYG on $85,000 salary"

→ Calculates using current ATO tax brackets

Optional: Add More Tax Skills

We have several tax-related skills:

npx skills-au add superannuation-guide -a claude npx skills-au add payg-withholding -a claude npx skills-au add fbt-calculator -a claude npx skills-au add cgt-calculator -a claude

Common Use Cases

Invoice Review

Paste an invoice and ask Claude to verify GST treatment:

"Review this invoice for GST compliance: [paste invoice]"

BAS Prep Checklist

"Generate a BAS preparation checklist for a small retail business"

Deduction Questions

"Can I claim my home office as a business expense?"

Important Notes

⚠️ Not Tax Advice

AI skills provide guidance based on general ATO rules. For complex situations, lodgement, or binding decisions, consult a registered tax agent or the ATO directly.

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