How to handle VAT allocation (different rates + shipping fees) in Medusa v2?

[la-ruee-vers-le-bois]

Hi Medusa team,

I’m building a B2B SaaS for firewood sellers in France, and I’ve hit a VAT issue in Medusa v2.

👉 Legal background (France):

In France, shipping fees are considered an accessory to the goods.

If an order contains items with different VAT rates (e.g. 10% for firewood, 20% for accessories), shipping fees must be split proportionally across these VAT rates.

Example: if I invoice €45 shipping TTC, I need to split it into 10% VAT and 20% VAT portions depending on the basket composition.

👉 Concrete example:

Product A: Firewood, €343.00 HT, VAT 10% → €34.30 VAT, total €377.30 TTC

Product B: Accessory, €100.00 HT, VAT 20% → €20.00 VAT, total €120.00 TTC

Subtotal HT = €443.00

Shipping = €45.00 TTC (≈ €40.91 HT + €4.09 VAT at 10% / €? HT + €? VAT at 20%)

In this case, I must allocate shipping proportionally:

Ratio of HT values: Firewood = 343 / 443 = 77.4%, Accessory = 100 / 443 = 22.6%

Shipping split:

Firewood share: €40.91 × 77.4% = €31.65 HT @10% → €3.17 VAT

Accessory share: €40.91 × 22.6% = €9.26 HT @20% → €1.85 VAT

Total shipping VAT = €5.02, so shipping TTC = €45.00

👉 My question:
How can I implement this VAT allocation logic in Medusa v2?

Right now, Medusa only lets me set one VAT rate per shipping method.

I’d need a way to either:

Dynamically split shipping into multiple line items with different tax rates, or

Override Medusa’s tax calculation for shipping to distribute VAT proportionally.

Is there a recommended way to do this in Medusa v2?
If not, do you suggest extending the tax service or creating a custom shipping service?

Thanks a lot 🙏