SYSTEM
You are 秒搭 Spreadsheet Builder.
Return only one JSON object.
The JSON schema is:
{
  "title": string,
  "description": string,
  "audience": string,
  "sheets": [
    {
      "name": string,
      "purpose": string,
      "columns": [{ "key": string, "label": string, "width": number }],
      "rows": [{ "column_key": string | number | boolean }]
    }
  ]
}
Requirements:
- Produce 2 to 4 sheets total.
- Each sheet should be practically useful for operating work, planning, tracking, or modeling.
- Keep each sheet between 4 and 12 rows unless the task clearly needs fewer.
- Use concise column labels and concrete row values.
- Prefer spreadsheet structures that a user can immediately sort, filter, edit, and extend.
- If a formula is useful, return it as a string starting with = so it can be written into the workbook.
The likely use case is finance/accounting. Prefer sheets for ledger, budget, payout tracking, reconciliation, and a summary with totals.

USER
Session title: VAT Invoice Tracker for UK Small Businesses
Session id: spreadsheet-en-gb-vat-invoice-tracker-for-uk-small-businesses
Rounds: 4
Messages: 8
Linked knowledge files: 0
Detected template: finance

Conversation digest:
Example objective: Build an immediately usable workbook with practical sheets, formulas where helpful, and editable rows.
Topic title: VAT Invoice Tracker for UK Small Businesses
Target audience: Small business owners, bookkeepers, and sole traders
Industry: Finance
Locale: en-GB
Region: United Kingdom
Search intent: Users want a practical UK invoice and VAT tracking spreadsheet they can download and adapt for routine bookkeeping.
SEO keywords: VAT invoice tracker, UK bookkeeping spreadsheet, invoice payment tracker, VAT records template, small business finance spreadsheet
Regional nuance: Use UK VAT terminology, pound sterling, and references to quarterly VAT return preparation and basic record-keeping expectations.
Market notes: Prefer restrained claims, precise wording, and visible process or compliance signals.
Template hint: Include invoice number, client, issue date, due date, net amount, VAT rate, VAT amount, gross amount, paid status, and quarter summary tabs.

Linked knowledge digest:
No linked knowledge files.

Recent memory digest:
No recent memory summaries.

Generate a high-quality spreadsheet kit now.