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Startup Check

Always run initialize at startup. If it returns online: false, alert the user that they are operating in offline mode.

Calculation Precision

Ensure all total and totalVAT fields are rounded to 2 decimal places.

$Total = (UnitPrice \times Quantity) - Discount$

Config Updates

If a sale response includes shouldDownloadLatestConfig: true, trigger a background call to refresh tax rates.

Unique Invoices

Never reuse a posInvoiceNumber, even for failed attempts, unless explicitly retrying the exact same payload.

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Troubleshooting

Symptom	Cause	Resolution
Connection Refused	Service not running	Check if the Windows Service or Kestrel console is active.
401 Unauthorized	Expired Token	Use /set-token or re-run the activation sequence.
Validation Errors	Data Mismatch	Verify taxRateId matches MRA global configurati