Customs App

Customs Surtax POC — Engineering README

Audience: Technical GenAI-Logic evaluators

Project: CBSA Steel Derivative Goods Surtax calculator, built as a proof-of-concept.

Run Instructions: at end

Creation Prompts

Requires 16.02.05, windows or mac.

🤖 Bootstrap Copilot by pasting the following into the chat

Please load `.github/.copilot-instructions.md`

🤖 To Create the system, paste this into the copilot chat

Create a fully functional application and database
 for CBSA Steel Derivative Goods Surtax Order PC Number: 2025-0917 
 on 2025-12-11 and annexed Steel Derivative Goods Surtax Order 
 under subsection 53(2) and paragraph 79(a) of the 
 Customs Tariff program code 25267A to calculate duties and taxes 
 including provincial sales tax or HST where applicable when 
 hs codes, country of origin, customs value, and province code and ship date >= '2025-12-26' 
 and create runnable ui with examples from Germany, US, Japan and China" 
 this prompt created the tables in db.sqlite.
  Transactions are received as a CustomsEntry with multiple 
SurtaxLineItems, one per imported product HS code.

🤖 Optionally, create the test suite

create behave tests from CBSA_SURTAX_GUIDE

Results: system, test suite and report

System: API, Database, Logic, Admin App

app

Test Suite and Report

The GenAI-Logic create command builds test services and Context Engineering. These enable the LLM to generate tests that proved the code worked, as well as elucidate the logic through readable test reports.

behave rpt

Run Instructions

Start the server, and enter a SurTax Order:

Country Origin: China
Province: ON
Order Number:

And a SurTaxLineItem:

Line #: 1
Quantity: 1
Price: 10000
HS Code: < the first>

ReQuery, and Verify Total Amount Due: 14125

Create from Gherkin

You can also create from Gherkin (Behave) test definitions:

``` As a customs calculation engine I want to determine when the CN 25‑28 25% surtax applies to imported goods that contain steel melted & poured in China or aluminum smelted & cast in China, and compute the surtax on the value for duty So that import declarations include accurate CN 25‑28 charges in addition to regular duties/taxes, with correct documentation rules and exemptions enforced. Feature: CN 25-28 Surtax Calculation (25% on value for duty) Background: Given the system can read "value for duty" as determined under sections 47–55 of the Customs Act # used as the base for CN 25-28 surtax And the shipment includes HS classification and documentary data for COM (country of melt & pour) and CSC (country of smelt & cast) And the system date reflects the importation date used by CBSA (incl. FPOA logic if required)

# Core applicability Scenario: Apply 25% surtax to steel melted and poured in China Given the goods are steel covered by Part 1 of the SOR/2025-154 Schedule And any portion of the raw steel was first produced in liquid state and poured into its first solid state in China When I calculate CN 25-28 Then I add a surtax of 25% of the value for duty And I record reason code "Steel – Chinese melt & pour (CN 25-28)" And I retain links to supporting documents # Source: CN 25-28; SOR/2025-154 s.2(1), s.3(1) (25% on value for duty) # 1 2

Scenario: Apply 25% surtax to aluminum smelted and cast in China Given the goods are aluminum covered by Part 2 of the SOR/2025-154 Schedule And either the largest or second-largest volume of primary aluminum was produced in China Or the aluminum was most recently liquified and cast into solid state in China When I calculate CN 25-28 Then I add a surtax of 25% of the value for duty And I record reason code "Aluminum – Chinese smelt & cast (CN 25-28)" # Source: CN 25-28; SOR/2025-154 s.2(2), s.4(1) # 1 2

# Deeming rule if documentation not provided Scenario: Deem steel subject to surtax when importer fails to provide proof Given the goods are subject steel And the importer fails to provide, when requested, acceptable proof that the steel is NOT melted and poured in China When I calculate CN 25-28 Then I deem the steel to contain Chinese melt & pour And I apply the 25% surtax on the value for duty # Source: Deeming provision for steel (certificate/report/invoice) # 1 2

Scenario: Deem aluminum subject to surtax when importer fails to provide proof Given the goods are subject aluminum And the importer fails to provide, when requested, acceptable proof that the aluminum is NOT smelted and cast in China When I calculate CN 25-28 Then I deem aluminum to be smelted & cast in China And I apply the 25% surtax on the value for duty # Source: Deeming provision for aluminum # 2

# Documentation timing rule (commercial invoice no longer sufficient after Sept 22, 2025) Scenario: Enforce stricter COM/CSC documentation on/after 2025-09-22 Given the importation date is on or after 2025-09-22 And the importer submits only a commercial invoice or "report" as proof of COM/CSC When I validate proof Then I reject it as insufficient for avoiding CN 25-28 And I require mill test certificates or equivalent technical certificates # Source: CN 25-28 update and industry guidance clarifying the 2025-09-22 cutoff # 3 4

# Exemptions and non-applicability Scenario: Exempt U.S.-origin goods Given goods originate in the United States per CUSMA marking regulations When I evaluate CN 25-28 Then I do not apply the 25% surtax # 1 4

Scenario: Exempt goods in transit before 2025-07-31 (with proof) Given the goods were in transit to Canada before 2025-07-31 and evidence is provided (e.g., bill of lading) When I evaluate CN 25-28 Then I do not apply the 25% surtax # 1 4

Scenario: Exempt CN 25-28 when Chapter 98 applies Given the goods are correctly classified under Chapter 98 of the Customs Tariff When I evaluate CN 25-28 Then I do not apply the 25% surtax even if the goods otherwise match Schedule items # 4

Scenario: Exempt low-value shipments under CAD 5,000 (per CAD) Given the cumulative value for duty of all CN 25-28 goods on a single Commercial Accounting Declaration is ≤ CAD 5,000 When I evaluate CN 25-28 Then I do not apply the 25% surtax # 5 6

# Interactions with other charges Scenario: Surtax is in addition to other duties and taxes Given the goods are subject to MFN/customs duty, SIMA AD/CVD, and GST/HST When I calculate totals Then I add CN 25-28 surtax on top of these other amounts (computed on value for duty) # 1 7

# HS coverage check Scenario: Apply only if HS classification is listed in the SOR/2025-154 Schedule (or Chapter 99 fallback) Given the HS code is present in Part 1 (steel) or Part 2 (aluminum) of the Schedule Or the goods fall under Chapter 99 but would otherwise fall under those parts When I evaluate applicability Then I proceed with CN 25-28 calculation as relevant Else I do not apply CN 25-28 # 2 8```