home / skills / cleanexpo / ato / payg_instalment_optimization
This skill analyzes PAYG instalment options, compares amount vs rate methods, and models GDP-adjusted impacts to help optimize tax timing.
npx playbooks add skill cleanexpo/ato --skill payg_instalment_optimizationReview the files below or copy the command above to add this skill to your agents.
---
name: payg-instalment-optimization
description: PAYG instalment strategy analysis — amount vs rate method, variation penalty risk, GDP adjustment
---
# PAYG Instalment Optimization Skill
Analyses PAYG instalment obligations and optimises the payment strategy. Compares amount method vs rate method, assesses variation penalty risk, and models the impact of GDP-adjusted rates.
## When to Use
- Reviewing quarterly PAYG instalment amounts
- Assessing whether to vary instalments (and penalty risk)
- Comparing amount method vs rate method
- Checking 85% safe harbour threshold
- Modelling scenarios for income fluctuations
- Annual instalment method election
## Methods
### Amount Method (s 45-112)
- ATO calculates instalment based on prior year tax
- Four equal quarterly payments
- Suitable for stable income
### Rate Method (s 45-115)
- ATO provides instalment rate (based on prior year)
- Apply rate to current quarter's instalment income
- Better for volatile or seasonal income
- GDP-adjusted rate may apply
## Variation Rules (s 45-205)
Taxpayers can vary instalment amounts if they believe actual tax will differ from calculated instalments. However:
### 85% Safe Harbour (s 45-235)
- If varied amount is **at least 85%** of actual tax, no penalty applies
- If under 85%, General Interest Charge (GIC) applies on shortfall
- GIC rate: base rate + 7% (compounding daily)
### Variation Risk Assessment
| Scenario | Risk | Recommendation |
|----------|------|---------------|
| Varied to > 85% of actual | None | Safe harbour applies |
| Varied to 75-85% of actual | Low | GIC on small shortfall |
| Varied to < 75% of actual | Medium | Significant GIC exposure |
| Varied to < 50% of actual | High | GIC + potential ATO attention |
## Engine Reference
- **Engine**: `lib/analysis/payg-instalment-engine.ts`
- **Function**: `analyzePAYGInstalments(tenantId, financialYear, options)`
- **Output**: Current method analysis, variation scenarios, penalty risk, recommendations
## Legislation
- TAA 1953, Division 45, Schedule 1 — PAYG instalment rules
- TAA 1953, s 45-112 — Amount method
- TAA 1953, s 45-115 — Rate method
- TAA 1953, s 45-205 — Variation of instalments
- TAA 1953, s 45-235 — Penalty safe harbour (85% rule)
- TAA 1953, s 8AAD — General Interest Charge rate
This skill analyses PAYG instalment obligations and recommends an optimal payment strategy. It compares the amount method and rate method, quantifies variation penalty risk, and models the effect of GDP-adjusted rates to support decision-making. The output highlights safe-harbour exposure and practical variation scenarios.
The engine evaluates historical tax, current income flows, and the ATO instalment rate to compare the amount versus rate approaches. It simulates variation choices and estimates shortfall exposure under the 85% safe-harbour rule, applying GIC assumptions where relevant. Scenarios include GDP-adjusted rate impacts and sensitivity to income volatility to produce clear recommendations.
What is the 85% safe-harbour?
If a varied instalment equals at least 85% of actual tax for the period, penalties do not apply; otherwise GIC applies to the shortfall.
When is the rate method preferable?
The rate method suits volatile or seasonal income because instalments track current receipts rather than last year’s tax.
How is penalty exposure estimated?
Exposure is modelled by comparing varied instalments to projected actual tax, then applying expected GIC to any shortfall using a conservative interest assumption.