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Engine

The Engine tab is the control plane for advanced tax. It does not define every tax rule itself, but it determines how the system should interpret and apply advanced behavior.

If a merchant uses advanced tax at all, this is the first tab they should understand.

What the Engine Controls​

The engine defines:

  • whether advanced tax is active
  • whether the store remains on manual fallback
  • the home country
  • default tax codes
  • shipping tax code behavior
  • how prices are interpreted
  • whether destination drives collection
  • whether threshold monitoring is active

Those choices affect how later tabs behave.

Mode​

The engine can operate in manual or advanced mode.

Manual Mode​

Manual mode means the merchant still relies on the store’s simpler manual tax policy even if advanced data exists.

This is useful when the merchant wants to prepare advanced tax in stages without switching live checkout immediately.

Advanced Mode​

Advanced mode means the engine is ready to become the primary logic layer for tax determination, subject to being enabled and having the necessary data.

Enabled at Checkout​

This switch answers a narrow operational question:

Should live checkout actively use advanced tax quotes?

If this is off, the merchant can still configure advanced tax without affecting live customers.

This is why the switch matters so much during rollout. It allows preparation before activation.

Home Country​

The home country anchors the engine’s default context. It is the primary country the merchant uses as the baseline for setup and simulator defaults.

The home country is not automatically the only country the merchant can operate in. It is the engine’s main reference point.

Default Tax Code​

The default tax code is the category the engine falls back to when a product does not have a more specific mapping.

This matters because advanced tax depends on tax codes to match products against rules. If the default is poorly chosen, unmatched products can still produce misleading outcomes.

Shipping Tax Code​

The shipping tax code determines how shipping is classified when the engine evaluates a checkout quote.

This is useful because shipping sometimes needs to behave like a separate taxable object rather than simply inheriting a product’s tax treatment.

Prices Entered With Tax​

This switch controls whether the engine should interpret catalog prices as already containing tax.

  • Turn it on when prices are entered as tax-inclusive.
  • Leave it off when prices are pre-tax and tax should be added afterward.

This setting should be aligned with the merchant’s real pricing strategy, not guessed from what “looks normal.”

Threshold Monitoring​

Threshold monitoring allows the engine to keep jurisdictions visible even before they are fully active for collection.

This is an operational planning tool. It helps the merchant prepare for expansion or track jurisdictions that are not yet live collection zones.

Destination-Based Collection​

This switch tells the engine to use the customer’s checkout destination as the primary tax decision input.

If this is off, the engine is less destination-driven and more static. If it is on, the merchant should make sure the relevant registrations and rules actually exist for the destinations they expect to serve.

How to Configure the Engine Safely​

The recommended sequence is:

  1. set the correct mode
  2. set the home country
  3. define the default and shipping tax codes
  4. align price interpretation with the real catalog pricing model
  5. decide whether destination should drive collection
  6. keep live checkout disabled until registrations and rules are validated

Common Errors​

Enabling the engine before rules exist​

If a merchant enables advanced tax without preparing the supporting data, checkout may produce fallback or warning-heavy outcomes that the team did not expect.

Using the wrong price interpretation​

If tax-inclusive pricing is configured as exclusive, totals appear inflated. If exclusive pricing is configured as inclusive, the tax line may look artificially low because the system is deriving tax from the existing price.

Treating destination logic as optional while expecting destination-specific outcomes​

If the merchant expects different results by location, destination-based collection and destination rules must be configured intentionally.

Best Practice​

Treat the Engine tab as the “policy switchboard” for advanced tax. It should be configured early, but it should not be the only thing configured before go-live.

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