invoice

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Generate professional invoices for clients using standardized templates with automatic invoice numbering and client management. This skill should be used when creating invoices for American Laboratory Trading, Empirico, Versa Computing, or other clients with tracked invoice histories.

arlenagreer By arlenagreer schedule Updated 6/8/2026
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name: invoice description: Generate professional invoices for clients using standardized templates with automatic invoice numbering and client management. This skill should be used when creating invoices for American Laboratory Trading, Empirico, Versa Computing, or other clients with tracked invoice histories.

Invoice Generation Skill

Overview

Generate professional HTML invoices using pre-configured templates for hourly and subscription billing. Track client information, automatically increment invoice numbers, and maintain invoice history across all clients.

⚡ First step, every invocation: Read LEARNINGS.md in this skill folder before doing anything else, and apply anything relevant. Last step, every invocation: capture any new durable lesson back into LEARNINGS.md (see Self-Improvement). This is how the skill gets better over time.

When to Use This Skill

Use this skill when:

  • Creating a new invoice for an existing client by name
  • Adding a new client to the invoice system
  • Viewing client information or invoice history
  • Generating invoices with work log entries (hourly) or subscription billing

Core Capabilities

1. Generate Invoice for Existing Client

When the user requests an invoice for a client by name:

  1. Load client data from clients.json to retrieve:

    • Client details and billing information
    • Invoice type (hourly or subscription)
    • Last invoice number for auto-increment

  2. For hourly invoices:

    • Request work log entries from the user (they will paste as text)
    • Parse work log format: Date - Project - Hours - Description
    • For Versa Computing, parse: Date - Project - Hours - Description with separate Project and Description columns
    • Calculate total hours and amount (hours × hourly_rate)

  3. For subscription invoices:

    • No work log needed
    • Use subscription_name and subscription_amount from client data

  4. Increment invoice number:

    • New number = last_invoice_number + 1
    • Format: {invoice_prefix}-{current_year}-{new_number:03d} (use the actual billing year, e.g. EMP-2026-005)

  5. Calculate dates:

    • Invoice date: Use current date (check system date in environment)
    • Due date: Invoice date + payment_terms_days

  6. Load appropriate template:

    • Hourly: assets/hourly-invoice-template.html
    • Subscription: assets/subscription-invoice-template.html

  7. Replace placeholders with client data:

    • {{INVOICE_NUMBER}}, {{INVOICE_DATE}}, {{DUE_DATE}}
    • {{CLIENT_NAME}}, {{CLIENT_ATTENTION}}, {{CLIENT_ADDRESS_LINE1}}, {{CLIENT_CITY_STATE_ZIP}}
    • {{PAYMENT_TERMS}} (e.g., "30" for Net 30)
    • {{PROJECT_REFERENCE}} or {{PO_NUMBER}} as applicable
    • For hourly: {{TOTAL_HOURS}}, {{HOURLY_RATE}}, {{SUBTOTAL}}, {{TOTAL_AMOUNT}}
    • For subscription: {{SUBSCRIPTION_NAME}}, {{BILLING_MONTH}}, {{AMOUNT}}
    • Work log entries (populate table rows in HTML)

  8. Special handling for Versa Computing:

    • Use 4-column work log table: DATE | PROJECT | DESCRIPTION | HOURS
    • Separate project name from description in work log entries
    • Project names go in the PROJECT column, descriptions in DESCRIPTION column

  9. Save invoice:

    • Filename format: Invoice-{invoice_number}-{short_name}-{month}-{year}.html
    • Location: User's Desktop (/Users/arlenagreer/Desktop/)

  10. Convert to PDF (automatic):

    • Always generate a PDF alongside the HTML using headless Chrome.
    • Command (same base filename, .pdf extension):
      "/Applications/Google Chrome.app/Contents/MacOS/Google Chrome" \
  --headless --disable-gpu --no-pdf-header-footer \
  --print-to-pdf="/Users/arlenagreer/Desktop/{invoice_filename}.pdf" \
  "file:///Users/arlenagreer/Desktop/{invoice_filename}.html"
    • Chrome respects the template's print CSS, so the PDF matches the styled layout.
    • If Chrome is unavailable, fall back to wkhtmltopdf {html} {pdf} and inform the user.
    • Confirm both the .html and .pdf were saved to the Desktop.

  11. Update clients.json:

    • Set last_invoice_number to new number
    • Set last_invoice_date to invoice date
    • Save changes to maintain accurate history

2. Add New Client

To add a new client to the system:

  1. Request necessary information:

    • Company name and contact details (attention, address)
    • Invoice type (hourly or subscription)
    • Invoice number prefix (3-letter abbreviation)
    • Billing rate (for hourly) or subscription amount
    • Payment terms in days
    • Special requirements (e.g., project column, PO number)

  2. Add new client object to clients.json following the existing structure

  3. Confirm client has been added successfully

3. View Client Information

To view or list clients:

  • Read clients.json and display client details
  • Show invoice history (last invoice number and date)
  • List all tracked clients

Client Database Structure

Client information is stored in clients.json in the skill folder. Each client entry includes:

Required fields (all clients):

  • name: Full client name
  • short_name: Abbreviated name for filenames
  • invoice_prefix: 3-letter invoice number prefix
  • invoice_type: "hourly" or "subscription"
  • company_name: Company name for invoice
  • attention: Contact attention line
  • address_line1: Street address
  • city_state_zip: City, state, and ZIP
  • last_invoice_number: Last invoice number sent (integer)
  • last_invoice_date: Date of last invoice (YYYY-MM-DD)
  • payment_terms_days: Payment terms in days (e.g., 30 for Net 30)

Hourly invoice fields:

  • hourly_rate: Billing rate per hour
  • project_reference: Default project name
  • requires_project_column: (optional) true if work log needs separate project column

Subscription invoice fields:

  • subscription_name: Name of subscription service
  • subscription_amount: Monthly subscription amount

Current Clients

  • American Laboratory Trading (INV prefix, hourly billing)
  • Empirico (EMP prefix, subscription billing)
  • Versa Computing (VER prefix, hourly billing with project column)

Invoice Templates

Hourly Invoice Template

Located at: assets/hourly-invoice-template.html

Features:

  • Two-page layout: invoice summary (page 1) and detailed work log (page 2)
  • Standard work log table: DATE | HOURS | DESCRIPTION
  • For clients requiring project column: DATE | PROJECT | DESCRIPTION | HOURS
  • Professional styling with Inter font and blue color scheme (#2563eb)
  • Print-optimized CSS

Placeholders to replace:

  • {{INVOICE_NUMBER}}, {{INVOICE_DATE}}, {{DUE_DATE}}
  • {{CLIENT_NAME}}, {{CLIENT_ATTENTION}}, {{CLIENT_ADDRESS_LINE1}}, {{CLIENT_CITY_STATE_ZIP}}
  • {{PAYMENT_TERMS}}, {{PROJECT_REFERENCE}}, {{PO_NUMBER}}
  • {{TOTAL_HOURS}}, {{HOURLY_RATE}}, {{SUBTOTAL}}, {{TOTAL_AMOUNT}}
  • Work log table rows (HTML tbody content)

Subscription Invoice Template

Located at: assets/subscription-invoice-template.html

Features:

  • Single-page layout
  • Simplified line items table: Description and Amount only
  • Same professional styling as hourly template

Placeholders to replace:

  • {{INVOICE_NUMBER}}, {{INVOICE_DATE}}, {{DUE_DATE}}
  • {{CLIENT_NAME}}, {{CLIENT_ATTENTION}}, {{CLIENT_ADDRESS_LINE1}}, {{CLIENT_CITY_STATE_ZIP}}
  • {{PAYMENT_TERMS}}, {{SUBSCRIPTION_NAME}}, {{PO_NUMBER}}
  • {{BILLING_MONTH}}, {{AMOUNT}}

Workflow Example

User: "Generate an invoice for Versa Computing"

Process:

  1. Read clients.json and locate Versa Computing client data
  2. Determine invoice type: hourly (requires work log)
  3. Prompt: "Please provide the work log entries for this invoice"
  4. User pastes work log text
  5. Parse entries, extracting: date, project, description, hours
  6. Calculate totals: sum hours × hourly_rate
  7. Increment invoice number: VER-2025-011 → VER-2025-012
  8. Calculate dates: invoice_date (today), due_date (today + 30 days)
  9. Load assets/hourly-invoice-template.html
  10. For Versa, use 4-column work log table format
  11. Replace all placeholders with client data and formatted work log entries
  12. Save to: /Users/arlenagreer/Desktop/Invoice-VER-2025-012-VersaComputing-Nov-2025.html
  13. Convert to PDF via headless Chrome (same name, .pdf)
  14. Update clients.json: set last_invoice_number to 12, last_invoice_date to today
  15. Confirm: "Invoice VER-2025-012 generated (HTML + PDF) and saved to Desktop. Ready for review."

Important Notes

  • Date handling: Always check the system date in <env> context (Today's date)
  • Work log parsing: Accept pasted text format, parse carefully to extract all components
  • Decimal hours: Use decimal format (0.5, 1.0, 2.5) not time format
  • Invoice numbering: Always auto-increment based on last_invoice_number
  • File location: Save all invoices to /Users/arlenagreer/Desktop/
  • PDF conversion: Always produce a .pdf next to the .html using headless Chrome (--print-to-pdf); the PDF is the send-ready artifact
  • No email sending: Skill generates the HTML and PDF files; user reviews and sends manually
  • Database updates: Always update clients.json after successful invoice generation
  • Template format: For Versa, modify table structure to include PROJECT column between DATE and DESCRIPTION

Self-Improvement (run after every invocation)

This skill is designed to learn. At the start of every invocation, read LEARNINGS.md and apply what's relevant. At the end of every invocation, reflect for a moment and record anything durable you discovered.

What counts as a learning worth saving

Save it when it will change how a future invoice is generated:

  • A client quirk or correction the user made (e.g., "Empirico has no PO number — omit the line", a preferred address, a rate change, a naming convention).
  • A tooling fact (e.g., which PDF engine works, a command flag that mattered, a path that differs from the docs).
  • A recurring formatting preference the user expressed.
  • A gap or ambiguity in these instructions that tripped you up, plus how it was resolved.

Do NOT save: one-off details specific to a single invoice (work-log contents, a particular month's hours), anything already captured in clients.json, or restatements of what SKILL.md already says.

How to record it

  1. Prefer fixing the source of truth. If the lesson is a permanent fact about a client → update clients.json. If it's a correction to the process or templates → edit SKILL.md / the template directly. Self-correcting the actual instructions is the highest form of improvement.
  2. Otherwise, append to LEARNINGS.md using the entry format defined there. Keep entries short, dated, and generalizable.
  3. Deduplicate and prune. If a new lesson supersedes an old one, edit the existing entry rather than stacking contradictions. Keep the file tight so it stays cheap to load every time.

Procedure at end of invocation

  • Ask yourself: "Did the user correct me, surprise me, or reveal a preference? Did anything in these instructions prove wrong or incomplete?"
  • If yes → apply step 1–3 above and briefly tell the user what you recorded (one line).
  • If nothing durable was learned, do nothing — don't pad the file with noise.
Install via CLI
npx skills add https://github.com/arlenagreer/claude_configuration_docs --skill invoice
Repository Details
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