[BUG] Gift Pro 12 months: wrong redemption mechanism + double VAT charge for Germany

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Redeeming a Gift Pro 12-month subscription on an existing active Pro account does not extend the subscription by 12 months as advertised. Instead, it converts the gift into a depleting credit balance — applied at net value only, stripping the VAT already paid at purchase. This results in two compounding problems:

Problem 1 — Wrong redemption mechanism:
The gift was converted into account credits rather than a subscription
extension. The credit covers only ~10.83 months, not 12 as promised.

• Credit applied to account: €195.00 net only (VAT stripped)
• Monthly drawdown: €18.00
• Effective coverage: €195.00 ÷ €18.00 = 10.83 months
• Shortfall vs. advertised: ~1.17 months (~€21)

Problem 2 — Double VAT:
VAT (19%) was paid at gift purchase (€37.05). Despite this, each monthly
billing cycle charges VAT again:

• Gift paid: €232.05 (€195.00 + €37.05 VAT at 19%)
• Monthly VAT charge: €3.42 (19% on €18.00)
• Over 12 months: €41.04 in duplicate VAT
• The original €37.05 VAT paid at purchase funds no service — it disappears

Total overcharge: ~€41.04 duplicate monthly VAT

• Account region: Germany
• Gift purchased: Gift Pro - 12 months
• Gift Invoice number A4E5SHFJ-0008
• Gift redeemed: 23 April 2026
• Gift period: 20 May 2026 – 20 May 2027
• Account monthly invoice number IZANWOQT-0002
• Existing subscription at time of redemption: Claude Pro (active, next renewal 20th May 2026)

What Should Happen?

Redeeming a 12-month gift on an active subscription should extend the renewal date by exactly 12 months (that's a contractual commitment) — next renewal pushed to 20 May 2027.
No additional monthly charges should occur during that period. No VAT should be charged monthly, as VAT was already collected at point of gift purchase.

Steps to Reproduce

Redeem a Claude Pro gift 1 Year subscription on claude.ai (web).
Account renewal date didn't extend.
The gift card turn into a depleting credit balance — applied at net value only, stripping the VAT already paid at purchase.

<img width="1007" height="328" alt="Image" src="https://github.com/user-attachments/assets/f44ec7f4-2992-401b-8f74-646d22de97eb" />

<img width="533" height="154" alt="Image" src="https://github.com/user-attachments/assets/fc6b6057-d0f2-4d61-835f-f406a0a24d63" />

Claude Model

None

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

1.5354.0

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_