vbrevik 🧾 Invoice Generator — Professional Invoice Builder
Generate complete invoices with line items, tax calculations, payment instructions, and structured data ready for PDF generation or email delivery.
Activation
When this skill activates, output:
🧾 Invoice Generator — Generating your invoice...
| Context | Status |
|---|---|
| User says "invoice", "generate invoice", "create invoice" | ACTIVE |
| User wants to bill a client for completed work | ACTIVE |
| User mentions line items, payment terms, or invoice numbers | ACTIVE |
| User wants a full contract (not just billing) | DORMANT — see contract-template |
| User wants financial projections (not invoicing) | DORMANT — see financial-model |
| User wants to onboard a new client | DORMANT — see client-onboarding |
Protocol
Step 1: Gather Inputs
Ask the user for:
- Your business info: Company name, address, email, phone, logo URL (optional)
- Client info: Client name, company, address, email
- Line items: Description, quantity, unit price for each item/service
- Payment terms: Net 15, Net 30, Net 60, due on receipt?
- Tax: Tax rate (%), tax ID/VAT number (optional)
- Discounts: Any discounts to apply? (% or fixed amount)
- Payment methods: Bank transfer, Stripe, PayPal, check?
- Invoice number format: Preference? (e.g., INV-2026-001, or auto-generate)
- Currency: USD, EUR, GBP, etc.
Step 2: Generate Invoice Number
Configurable formats:
| Format | Example | Best For |
|---|---|---|
| Sequential | INV-001 | Simple, solo freelancer |
| Year-sequential | INV-2026-001 | Annual tracking |
| Client-prefixed | INV-ACME-001 | Multi-client businesses |
| Date-based | INV-20260301-001 | High volume, daily tracking |
| Project-based | INV-PROJ42-001 | Per-project billing |
Auto-generation logic:
Format: [PREFIX]-[YEAR]-[SEQ]
Example: INV-2026-001
Next invoice: Check last invoice number, increment sequence.
If new year: reset sequence to 001.
Step 3: Calculate Totals
Build the invoice calculation:
── LINE ITEMS ─────────────────────────────
# Description Qty Rate Amount
1 [item description] [qty] $[rate] $[amount]
2 [item description] [qty] $[rate] $[amount]
3 [item description] [qty] $[rate] $[amount]
───────────────────────────────────────────
Subtotal: $[subtotal]
Discount (X%): -$[discount]
Subtotal after discount: $[after_discount]
Tax (X%): $[tax]
─────────────────
TOTAL: $[total]
Calculation rules:
- Subtotal = Σ (quantity × unit_rate) for each line item
- Discount applied to subtotal (before tax)
- Tax calculated on discounted subtotal
- Total = discounted subtotal + tax
- Round all amounts to 2 decimal places
- Display currency symbol consistently
Step 4: Payment Instructions
Generate payment details based on selected methods:
Bank Transfer:
── PAYMENT BY BANK TRANSFER ───────────────
Bank: [bank name]
Account name: [name]
Account number: [number]
Routing number: [number]
SWIFT/BIC: [code] (for international)
Reference: [invoice number]
Stripe Payment Link:
── PAY ONLINE ─────────────────────────────
Pay securely via credit card:
[Stripe payment link URL]
PayPal:
── PAYPAL ─────────────────────────────────
Send payment to: [email]
Reference: [invoice number]
Check:
── PAY BY CHECK ───────────────────────────
Make payable to: [company name]
Mail to: [address]
Memo: [invoice number]
Step 5: Due Date & Late Fee Terms
Due date calculation:
| Terms | Due Date | Late Fee |
|---|---|---|
| Due on receipt | Invoice date | 1.5%/month after 7 days |
| Net 15 | Invoice date + 15 days | 1.5%/month after due date |
| Net 30 | Invoice date + 30 days | 1.5%/month after due date |
| Net 60 | Invoice date + 60 days | 1.0%/month after due date |
| Custom | [specific date] | [custom terms] |
Late fee clause:
A late fee of [X]% per month ([Y]% annually) will be applied to
balances unpaid after the due date. Partial months are prorated.
Step 6: Professional Layout
Define the invoice layout structure:
┌─────────────────────────────────────────┐
│ [LOGO] INVOICE │
│ [Your Company] Invoice #: [num] │
│ [Your Address] Date: [date] │
│ [Your Email] Due: [due date] │
│ [Your Phone] Terms: [terms] │
├─────────────────────────────────────────┤
│ BILL TO: │
│ [Client Name] │
│ [Client Company] │
│ [Client Address] │
│ [Client Email] │
├─────────────────────────────────────────┤
│ # │ Description │ Qty │ Rate │ Amt │
│ ──┼────────────────┼─────┼──────┼───── │
│ 1 │ [item] │ [q] │ $[r] │ $[a] │
│ 2 │ [item] │ [q] │ $[r] │ $[a] │
│ 3 │ [item] │ [q] │ $[r] │ $[a] │
│ ──┴────────────────┴─────┴──────┴───── │
│ Subtotal: $[sub] │
│ Discount: -$[disc] │
│ Tax (X%): $[tax] │
│ ───────────────────── │
│ TOTAL DUE: $[total] │
├─────────────────────────────────────────┤
│ PAYMENT INSTRUCTIONS: │
│ [payment method details] │
├─────────────────────────────────────────┤
│ NOTES: │
│ [optional notes — thank you message, │
│ project reference, etc.] │
│ │
│ TERMS: │
│ [late fee policy] │
└─────────────────────────────────────────┘
Step 7: Structured Data Output
Generate invoice as structured JSON for programmatic use:
{
"invoice_number": "INV-2026-001",
"date": "2026-03-01",
"due_date": "2026-03-31",
"terms": "Net 30",
"currency": "USD",
"from": {
"name": "Your Company",
"address": "123 Main St, City, State 12345",
"email": "billing@company.com",
"phone": "+1-555-0100",
"tax_id": "XX-XXXXXXX"
},
"to": {
"name": "Client Name",
"company": "Client Corp",
"address": "456 Oak Ave, City, State 67890",
"email": "accounts@client.com"
},
"line_items": [
{
"description": "Web Development",
"quantity": 40,
"unit": "hours",
"rate": 150.00,
"amount": 6000.00
}
],
"subtotal": 6000.00,
"discount": { "type": "percentage", "value": 10, "amount": 600.00 },
"tax": { "rate": 8.25, "amount": 445.50 },
"total": 5845.50,
"payment_methods": ["bank_transfer", "stripe"],
"notes": "Thank you for your business!",
"late_fee": "1.5% per month on overdue balances"
}
Step 8: Email Template
Provide email copy for sending the invoice:
Subject: Invoice [INV-NUMBER] from [Your Company] — Due [Due Date]
Hi [Client First Name],
Please find attached invoice [INV-NUMBER] for [brief description of work].
Amount due: $[TOTAL]
Due date: [DUE DATE]
Payment: [payment method summary]
If you have any questions about this invoice, please reply to this email.
Thank you for your business!
[Your Name]
[Your Company]
[Your Phone]
Step 9: Output
Present the complete invoice package:
━━━ INVOICE: [Invoice Number] ━━━━━━━━━━━━
── INVOICE DETAILS ────────────────────────
From: [your company]
To: [client]
Date: [date]
Due: [due date]
Terms: [payment terms]
── LINE ITEMS ─────────────────────────────
[formatted line item table]
── TOTALS ─────────────────────────────────
Subtotal: $[amount]
Discount: -$[amount]
Tax: $[amount]
Total: $[amount]
── PAYMENT INSTRUCTIONS ───────────────────
[payment method details]
── STRUCTURED DATA (JSON) ─────────────────
[complete JSON for programmatic use]
── EMAIL TEMPLATE ─────────────────────────
[ready-to-send email copy]
── NOTES ──────────────────────────────────
[thank you message + late fee terms]
Inputs
- Business info (name, address, email, phone)
- Client info (name, company, address, email)
- Line items (description, quantity, rate)
- Payment terms and methods
- Tax rate and discount (optional)
- Currency and invoice number format (optional)
Outputs
- Unique invoice number with configurable format
- Calculated totals (subtotal, discount, tax, total)
- Payment instructions for selected methods (bank, Stripe, PayPal, check)
- Due date with late fee terms
- Professional layout template
- Structured JSON data for PDF generation or API integration
- Email template for invoice delivery
Level History
- Lv.1 — Base: Configurable invoice numbering (5 formats), line item calculation with discount and tax, multi-method payment instructions (bank/Stripe/PayPal/check), due date calculation with late fee terms, professional layout template, structured JSON output, email delivery template. (Origin: MemStack v3.2, Mar 2026)