In B2B commerce, especially in the hospitality and restaurant sector, buyers are accustomed to browsing product prices without VAT included .

However, at checkout, they expect to see the correct final total including VAT , calculated based on:

• Supplier location

• Buyer VAT status

• Intracommunity rules

• EU tax exemptions

The browsing experience reflects common B2B expectations with this new feature and setting:

• Product listing prices → Without VAT

• Checkout totals → With VAT (calculated properly)

Behavior

Browsing Phase (Pre-Checkout)

Displayed price per product:

Net price (Excluding VAT)

Optional label:

Excl. VAT

Checkout Phase

Display include:

• Net subtotal

• VAT amount (per rate if applicable)

• Total including VAT

• Tax exemption messaging if applicable

What will happen in your client's WhatsApp

1. ✅ When B2B + Show Without VAT = Active → Articles display net prices

2. ✅ Cart line items show net prices

3. ✅ Checkout shows full VAT breakdown

4. ✅ Final payable amount always includes VAT (unless exemption logic applies)

5. ✅ VAT calculation logic remains unchanged

6. ✅ No regression in B2C shops

7. ✅ No regression when “Show Articles Without VAT” is disabled

8. ✅ Works with:

   • Multiple VAT rates

   • Intracommunity VAT reverse charge

   • VAT exempt customers

9. ✅ Currency formatting remains correct

Edge Cases 

• Mixed VAT rate products

• Customer with valid EU VAT number

• Customer without VAT number

• Supplier inside EU vs outside EU

• VAT reverse charge scenario

• Customer switches country mid-checkout

• Rounding differences between net display and final total

• Discount codes applied

• Quantity changes in cart

Business Rationale

The Restaurants and professional buyers think in net pricing.

Forcing VAT-inclusive browsing:

• Breaks B2B expectation

• Reduces clarity

• Feels retail (B2C)

This change aligns OrderLemon Catalogue with:

• Supplier platforms

• Wholesale marketplaces

• Professional procurement systems

Now we enter the fun territory: tax logic. The place where tiny assumptions grow fangs.

Important principle:

Display mode changes. Tax engine does not.

1. Activation Logic

Feature is active ONLY if:

• B2B is active in your shop

Otherwise OrderLemon behaves normally (VAT-inclusive browsing if that was default).

2. Price Model Assumption

Every product must internally store:

• net price

• vat rate

• gross price = net_price * (1 + vat_rate)

If the system currently stores only gross, you must reverse-calculate:

net price = gross_price / (1 + vat rate)

3. Browsing Phase Logic (Listing / PDP / Cart Items)

When feature is active:

Display:

display_price = product.net_price
label = "Excl. VAT"

Cart Line Total:

line_total_display = quantity * net_price

No VAT breakdown shown in browsing.

Important:

This is pure UI logic. The cart internally must still carry:

line_net

line_vat
line_gross
vat_rate

Even if VAT isn’t displayed yet.

4. Checkout Tax Calculation Logic

At checkout, VAT must be recalculated based on:

• Supplier country

• Customer billing country

• Customer VAT number validity

• EU membership status

• Reverse charge rules

Here is the decision matrix simplified.

5. VAT Decision Matrix (EU Context)

Let:

• SC = Supplier Country

• CC = Customer Country

• VAT_ID = Valid VAT number provided?

• EU(SC) / EU(CC) = Is country in EU?

Case A — Same Country

SC == CC

Result:

• Apply local VAT

• Customer pays VAT

• Show:

  • Net

  • VAT

  • Gross

Case B — Both in EU, Different Countries

EU(SC) == true

EU(CC) == true

SC != CC

Now split:

B1 — Valid VAT ID Provided

Reverse charge applies.

Result:

• VAT rate = 0%

• Show:

  • Net subtotal

  • VAT = 0

  • Message: “Reverse charge applied”

• Invoice must mention reverse charge directive

B2 — No Valid VAT ID

Apply supplier country VAT.

Result:

• VAT added

• Customer pays VAT

Case C — Supplier in EU, Customer Outside EU

EU(SC) == true

EU(CC) == false

Usually export scenario.

Result:

• VAT = 0%

• Show export message

But confirm compliance rules per country (implementation config-based).

Case D — Supplier Outside EU

Country-specific logic required.

Default safe assumption:

• Tax rules determined by supplier configuration.

This should be configurable.

6. Checkout Calculation Flow

Pseudo logic:

function calculateCheckout(cart, customer, supplier):




    for each line in cart:

        vat_rate = determineVATRate(customer, supplier, line.product)




        line.net = line.quantity * line.product.net_price

        line.vat = line.net * vat_rate

        line.gross = line.net + line.vat




    subtotal_net = sum(line.net)

    total_vat = sum(line.vat)

    total_gross = sum(line.gross)




    return {

        subtotal_net,

        total_vat,

        total_gross,

        breakdown_per_rate

    }

Notice:

VAT rate determination happens at checkout, not browsing.

7. Rounding Strategy (Critical)

Never round per unit before multiplying.

Correct:

line_net = round(quantity * unit_net, 2)

line_vat = round(line_net * vat_rate, 2)

Wrong:

round(unit_net * vat_rate) * quantity

Rounding per unit causes cumulative discrepancies.

Always round at line level.

8. Cart Behavior While Browsing

Even though browsing shows net prices:

Internally store:

cart_line = {

  product_id,

  quantity,

  unit_net,

  vat_rate_snapshot,

  unit_gross_snapshot
}

But do NOT trust vat_rate_snapshot at checkout.

Revalidate VAT at checkout using customer data.

Taxes are contextual, not static.

9. UI Display Summary

Browsing:

• Net prices only

• “Excl. VAT” indicator

Checkout:

• Net subtotal

• VAT per rate

• Total VAT

• Grand total incl. VAT

• Reverse charge or exemption messaging if applicable

10. Edge Conditions That Will Break Production If Ignored

Mixed VAT rates in cart

Discount codes (percentage vs fixed)

Shipping VAT rate different from product VAT

Manual price overrides

Currency rounding in multi-currency shops

Customer changing VAT ID mid-checkout

Country change after VAT validated

Tax is not arithmetic. It’s conditional law disguised as arithmetic.