Digital Subscription Invoice¶

¶

1. Objective¶

Issue every coach a GST-compliant, paper-less invoice for subscription purchases & renewals.
Each invoice is delivered as

a responsive web page (/invoice/{slug})
a downloadable PNG “invoice screenshot” (lightweight, print-ready)
a QR code for instant verification or ledger lookup (Good to have not mandatory)
an auto-number that encodes year, month, day and a monthly running sequence.

2. Tax Logic¶

Billing State	Tax Applied	Rate
Haryana	CGST 9 % + SGST 9 %	18 %
Other Indian states	IGST 18 %	18 %

Exactly one bucket (CGST/SGST or IGST) is non-zero per invoice.

3. Invoice Numbering¶

Format: FTPP/YYYY/MM/SEQ - For Offline Sales Format: FTPPON/YYYY/MM/SEQ- for Online Sales

FTP – static prefix
YYYY – four-digit year
MM – month (01-12)
DD – issue day
SEQ – counter that resets on the 1st of each month

Example, 6 Apr 2025, third invoice that month → FTP/2025/04/3

Generation (atomic)¶

today  = LocalDate.now()          # IST
prefix = "FTPP/" + YYYY + "/" + MM + "/"

seq = get_next_sequence(prefix)   # 1,2,… resets monthly
invoice.number = prefix + seq

4. User Stories¶

ID	Role	Story	Acceptance
U1	Coach	Need a clear digital invoice I can save/print.	Opens URL → sees invoice → downloads PNG
U2	Finance	Require GST fields & correct monthly series number.	Number = `FTPP/YYYY/MM/SEQ`; GST shown

5. Functional Requirements¶

5.1 Invoice Generation¶

Triggered on successful subscription purchase/renewal.
Captures coach details, plan, seats, discounts, tax, total.
Number generated as per 4 (monthly sequence).
Stores JSON → renders HTML → PNG.

5.2 Web Invoice Page¶

Sections: company header • bill-to block • item table • tax & total • QR • buttons Download PNG / Print
Mobile-first.

5.3 PNG Screenshot¶

Aspect	Spec
Viewport	eg. 1440 × 2048 px (design will provide this)
Output	eg PNG, ≤ 350 kB
Storage	S3 / CDN (`image_url`)

5.4 QR Code (if generated)¶

Signed JWT payload {invoice_id, coach_id, amount, status} (90-day expiry) → /verify/{token} endpoint.

5.5 Delivery¶

Email (HTML), WhatsApp template (opt-in), in-app.

5.6 Finance Exports / API¶

Date-range CSV/JSON/ZIP(PNG); REST GET /api/v1/invoices this is needed for finance in admin panel.

6. Data Model (gxample)¶

Field	Type	Notes
`invoice_id`	UINT	PK
`number`	VARCHAR(32)	`FTPP/YYYY/MM/SEQ` (SEQ resets monthly)
`coach_id`	UINT	FK
`billing_state`	VARCHAR(2)	“HR”, “UP”…
`subtotal`	DEC(10,2)	ex-tax
`cgst`, `sgst`, `igst`	DEC(10,2)	Only one set non-zero
`total`	DEC(10,2)	payable
`status`	ENUM(Pending/Paid/Cancelled)
`issue_date`, `due_date`	DATE
`web_slug`	CHAR(32)	unguessable
`image_url`	VARCHAR	PNG key

7. System Flow¶

sequenceDiagram
    participant App   as Coach App
    participant BE    as Backend
    participant CDN   as S3 / CDN
    participant Coach as Coach Device

    App->>BE: Purchase / Renewal
    BE->>BE: Create invoice (FTPP/YYYY/MM/SEQ)
    BE->>CDN: Upload HTML invoice
    BE-->>App: Snackbar “Invoice ready”
    BE-->>Coach: Email / WhatsApp link
    Coach->>CDN: View invoice page
    Coach->>CDN: Download invoice (optional)

8. QA Checklist¶

Number follows FTPP/YYYY/MM/SEQ; SEQ resets on 1st of each month.
Haryana → CGST + SGST; others → IGST.
PNG ≤ 350 kB,