The Markdown Invoice Generator is not a tool for freely styling arbitrary Markdown documents, but a lightweight parser for invoices that recognizes predefined heading names as sections.

A line starting with # is treated as the document title (such as # Invoice), and content under ## Destination, ## Publisher, ## Billing information, ## Transfer destination (or the legacy heading Payment address), and ## Item is displayed in the corresponding positions of the A4-style preview on the right.

Destination, publisher, and transfer destination sections display non-empty lines in sequence. Billing information removes leading hyphens from each line to form a list, allowing users to write necessary item labels such as "Invoice Number:", "Issue Date:", and "Due Date:".

The tool does not perform semantic analysis on item labels, nor does it validate date formats or invoice number duplicates. Retaining the template while replacing only the body text of each section helps preserve the document structure.

There is no validation requiring all of these sections to be present. Empty sections simply remain blank in the preview. Because required items vary depending on commercial transactions and legal frameworks, you must distinguish between "no errors are displayed" and "all necessary information is present."

The ## Item section (along with supported English section aliases) is parsed as a pipe-delimited Markdown table requiring a delimiter separator row with --- while the table header row is optional, with data rows containing exactly four cells and optional outer trailing pipes accepted.

Each item row must supply a non-empty name, while unit prices and quantities must be finite, non-negative decimal numbers; commas, currency symbols like yen, and extra whitespace are stripped, but negative numbers, Infinity, and scientific notation are rejected.

The tax rate column must explicitly specify either 8 or 10 (with or without %); empty, NaN, zero, or unrecognized tax rates trigger line-numbered errors instead of defaulting to 10%.

Aggregate or line overflows are checked, though validation covers only the recognized Item section and its specified structural, numeric, and tax rate rules.

Missing sections are not required. While reported errors exist, document preview is unavailable and application Print buttons are disabled until corrected.

Note that validation is limited to these specific parser rules rather than full document content or legal compliance; make sure to review the formatted preview and markdown source before issuing.

Under the strict table parser adapted with English section aliases, item rows require a table separator and exactly four cells, though an optional outer trailing pipe is accepted.

Item names must not be empty. Unit prices and quantities are parsed as finite, non-negative decimal numbers after commas, yen symbols, and whitespace are stripped; scientific notation, Infinity, and negative values are strictly rejected.

Tax rates must explicitly specify either 8 or 10 (with optional % signs and whitespace); blank rates, NaN, zero, and other percentages trigger explicit parsing errors rather than defaulting to 10.

Both per-line amounts and aggregate totals are checked against numeric overflow, while valid 8% and 10% totals remain unchanged. Decimal quantities can still be entered, but tax-exempt items, zero tax, and custom rates remain unsupported.

Any detected syntax or numeric defect produces a line-numbered error, replaces the document preview with an error notice, and disables printing until corrected.

The invoice generator applies validation modeled on the core parser, supporting English section aliases while requiring standard table separator delimiters—with table header rows remaining optional—and enforcing four-cell item rows with optional outer trailing pipes permitted.

Rather than silently skipping malformed lines or defaulting irregular tax rates, the parser mandates non-empty item names, explicit tax rates of 8 or 10 (accepting % signs), and finite, non-negative numbers for unit prices and quantities with commas, yen symbols, and whitespace stripped.

Negative values, exponential notation, Infinity, zero tax, blank rates, delimiter defects, cell mismatches, and overflow conditions trigger line-numbered error alerts.

Missing sections are not required, but while reported errors exist, document preview is unavailable and application Print buttons are disabled until corrected.

Built-in validation checks only the recognized Item section and its specified structural, numeric, and rate rules rather than legal compliance or overall document content, so you should always review the generated preview and source text before issuing an invoice.

The amount for each line item is unit price × quantity. Subtotals are calculated separately for items subject to 8% tax and items subject to 10% tax.

The 8% tax amount is calculated as 8% subtotal × 0.08, and the 10% tax amount is calculated as 10% subtotal × 0.10, with JavaScript's Math.floor applied once to each subtotal to truncate decimals.

The total consumption tax amount is the sum of the two tax amounts, and the total billing amount is the sum of the tax-exclusive subtotal and the total tax amount.

For example, if the 8% eligible subtotal is 1,011 yen, the candidate tax of 80.88 yen is truncated to 80 yen, and if the 10% eligible subtotal is 2,019 yen, 201.9 yen is truncated to 201 yen, resulting in a total tax amount of 281 yen.

Because this does not round tax on each individual line before summing, results may differ from invoices adopting different rounding conventions.

These calculation rules represent the display specification of this tool. They do not automatically reflect agreements with business partners, billing units, discounts, returns, foreign currencies, withholding taxes, eligibility determination for reduced tax rates, or accounting software rounding configurations.

Verify formal amounts against contract terms and applicable Japanese accounting and tax rules.

Edits are re-parsed in real time as you type, updating the document preview whenever your markdown table remains valid. The parser verifies that the recognized Item table possesses a required separator delimiter—with the header row remaining optional—and data rows containing four cells, with non-empty item names, finite non-negative unit prices and quantities, and explicit tax rates of 8% or 10%.

If a line contains negative numbers, scientific notation, Infinity, missing columns, or invalid rates, line-numbered error diagnostics appear immediately.

Missing sections are not required, but while reported errors exist, document preview is unavailable and application Print buttons are disabled until corrected.

Validation is focused on these specific structural, numeric, and rate rules rather than legal compliance or all document content, making it important to review the rendered preview and source markdown before issuing your invoice.

Format checks are minimal and do not validate document semantics. Formats and authenticity of recipient postal codes, issue dates, payment deadlines, bank accounts, qualified invoice registration numbers, or phone numbers are not verified.

Billing information is handled as simple display lines, so no warning is issued even if a payment deadline precedes the issue date.

Before printing, inspect the preview and cross-check typos, amounts, dates, transfer destinations, and payee names against source documents.

Resetting to the default template replaces the entire current Markdown with sample text. There is no auto-save or edit history, so save your draft elsewhere before resetting during editing.

Company names, addresses, bank accounts, registration numbers, and invoice numbers in the template are input examples and do not imply real-world existence or availability.

The print button calls window.print to open the standard browser print dialog. This tool does not directly generate or download a PDF binary.

If the browser or operating system provides a "Save as PDF" destination, the user can select it. A physical printer can also be selected.

Print CSS hides the operational interface and formats the invoice section for paper, but long addresses, numerous items, browser fonts, margins, and scale factors may prevent it from fitting on a single A4 page.

There is no fine-grained control over page break positions or repeating headers on multiple pages. In the print dialog, verify paper size, orientation, margins, scale, and background printing settings.

When saving as a PDF, open the saved file to inspect text clipping, overlapping lines, missing items, and total amounts. This tool does not guarantee consistent print rendering across different browsers, nor does it guarantee compliance with long-term PDF archiving requirements, electronic signatures, or tamper prevention.

Whether an invoice satisfies the mandatory items for Japan's qualified invoice (tekikaku seikyusho) system, the validity of registration numbers, tax rate breakdowns, transaction dates, recipients, and retention methods must be verified against the final document and transaction circumstances.

This tool does not query external databases for entered registration numbers, nor does it judge missing required items or statutory compliance.

Generating a PDF via browser printing does not mean that Electronic Bookkeeping Act (Denshi Choho Hozonho) or other statutory storage requirements are met.

Conditions necessary for business operations—such as searchability, correction and deletion logs, retention periods, and ensuring authenticity and visibility—must be established separately.

Regulations and formats may change, so verify official announcements and expert guidance valid at the time of issuance.

The ability to select the 8% reduced tax rate does not mean the tool has verified that the entered item qualifies for Japan's reduced tax rate.

Users must specify the tax category for each item. Because classification can vary depending on transaction conditions even under the same product name, cross-check goods and services against source documentation.

Tax-exempt or non-taxable items cannot be represented in this tool's tax rate column and require alternative invoice creation methods.

The invoice generator enforces strict numeric guards that reject negative unit prices, negative quantities, scientific notation, and Infinity, preventing malformed values from distorting invoice arithmetic.

Consequently, transactions involving discounts, returns, or adjustments cannot be entered as negative credit rows and must be accounted for separately.

All unit prices and quantities must be finite, non-negative decimal values, from which commas, yen symbols, and whitespace are stripped prior to calculation.

Tax rates must explicitly state 8 or 10 percent; blank entries, zeros, or alternative rates are flagged as errors rather than defaulted.

Both line amounts and aggregate totals are protected by overflow checks, and any syntax or numeric violation halts preview generation and disables printing via line-numbered error notices.

Currency displays are formatted in yen; when decimal quantities or tax rates produce fractional amounts, users should confirm that calculated figures conform to their commercial terms, as the tool provides no formal tax or legal-compliance guarantees.

The tool does not perform version control for post-issuance modifications, invoice numbering, duplicate issuance prevention, sending, payment reconciliation, or receipt generation.

There is no storage feature to restore drafts after closing the screen, so store Markdown drafts and output PDFs using organizational document management procedures if needed.

Although transfer destinations and addresses can display arbitrary text lines, handle confidential information according to your environment and organizational policies.

The fact that this component does not store data externally does not imply that overall network communication, including browser extensions or page delivery, is absent.

Operational precautions, such as not leaving input on shared devices, are necessary.

This tool is a drafting aid for styling structured Markdown and checking calculations across 8% and 10% tax rates. Do not issue documents merely because no errors appear; ensure a person conducts final checks against original order details, accounting records, client information, tax calculations, and statutory invoice requirements before printing or saving.