lunarfront-app/planning/12_Domain_Accounting_Journal_Entries.md

LunarFront Platform

Domain Design: Accounting & Journal Entries

Version 2.0 | Updated 2026-03-30

1. Overview

The Accounting domain ensures every financial event in the platform produces correct double-entry journal entries following Generally Accepted Accounting Principles (GAAP). The platform does not replace QuickBooks — it generates journal entries that the business's accountant imports into QuickBooks on a regular schedule (daily, weekly, or monthly).

This is the Hybrid approach: the platform owns all operational financial data and generates the accounting records. QuickBooks owns the general ledger, financial statements, and tax reporting. The accountant works in a familiar tool. No real-time API dependency on QuickBooks is required.

1.1 Accounting Standards

The system implements:

• Double-entry bookkeeping — every transaction produces balanced debit/credit entries. Total debits must always equal total credits.
• GAAP revenue recognition — revenue recorded when earned, not when cash received (accrual basis). Deferred revenue tracked as a liability until earned.
• Matching principle — COGS recorded at the same time as the related revenue.
• Immutability — journal entries are never modified or deleted. Corrections are made via reversing entries only.
• Contra accounts — discounts and returns tracked separately from gross revenue for full visibility.
• Materiality — the system tracks every transaction. Rounding differences handled via the Cash Over/Short account.

1.2 Accounting Basis

The system generates entries on an accrual basis — revenue is recognized when earned, expenses when incurred, regardless of when cash changes hands. This is the GAAP standard.

For businesses that file taxes on a cash basis (most small businesses), the accountant handles the conversion in QuickBooks. The platform provides both cash-flow reports (cash basis visibility) and accrual-based journal entries. This is the standard approach for small businesses: operate on accrual internally, file on cash basis.

1.3 Scope

Responsibility	Owner
Operational records	Platform — transactions, rentals, lessons, repairs, discounts, drawer
Journal entry generation	Platform — automatic on every financial event
Journal entry export	Platform — CSV export by date range, importable to QuickBooks
General ledger	QuickBooks — accountant imports exported entries
Financial statements	QuickBooks — P&L, balance sheet, tax reporting
Chart of accounts	Defined in platform, configurable per business to match QB setup
Payroll	External — ADP, Gusto, etc. Platform tracks hours/sessions for export only

1.4 Currency

The system operates in USD only. Single-currency assumption. Multi-currency support is out of scope — if needed in the future, it would require a separate currency layer with exchange rate tracking and foreign currency translation accounts.

2. Chart of Accounts

The chart of accounts is defined in the platform and is business-configurable. Account codes and names should match the business's existing QuickBooks chart of accounts exactly to ensure clean imports. Default codes are provided below as a starting point.

Businesses can rename accounts, add custom accounts, and deactivate unused accounts. They cannot delete accounts that have journal entry references.

2.1 Assets

Code	Account Name	Notes
1000	Cash - Register Drawer	Physical cash in main register
1010	Cash - Mobile POS	Mobile POS cash (trade shows, events)
1020	Cash - Safe	Cash moved from drawer to secure storage
1100	Accounts Receivable	Amounts owed by customers
1200	Payment Clearing	Card payments received but not yet settled by processor
1300	Inventory - Sale Stock	Products held for sale
1310	Inventory - Rental Fleet	Items held for rental (industry-specific module)
1320	Inventory - Parts & Supplies	Repair parts and consumables

2.2 Liabilities

Code	Account Name	Notes
2000	Sales Tax Payable	Tax collected from customers, owed to taxing authority
2100	Deferred Revenue - Rentals	Rental payments received for future periods
2110	Deferred Revenue - Lessons	Lesson payments received for future periods
2120	Deferred Revenue - RTO Equity	Rent-to-own equity portion — not earned until buyout
2200	Rental Deposits Held	Security deposits — liability until returned or applied
2300	Customer Credits	Store credits, makeup lesson credits, overpayments
2350	Gift Card Liability	Gift cards sold but not yet redeemed (module)
2400	Unearned Repair Revenue	Deposits on repairs not yet completed
2500	Accounts Payable	Amounts owed to vendors/suppliers

2.3 Revenue

Code	Account Name	Notes
4000	Sales Revenue - Category 1	Primary product category (configurable name)
4010	Sales Revenue - Category 2	Secondary product category (configurable name)
4020	Sales Revenue - Category 3	Tertiary product category (configurable name)
4100	Rental Revenue	Monthly rental income earned
4200	Lesson Revenue	Lesson income earned
4300	Repair Revenue - Labor	Repair labor charges
4310	Repair Revenue - Parts	Parts billed to customer
4400	RTO Buyout Revenue	Recognized on rent-to-own completion
4500	Other Income	Kept deposits, late fees, misc

2.4 Contra Revenue

Code	Account Name	Notes
4900	Sales Discounts	Discounts applied at POS — keeps gross revenue clean
4910	Sales Returns & Refunds	Returned merchandise and refunded amounts
4920	Proration Credits Issued	Billing date change credits

2.5 Cost of Goods Sold

Code	Account Name	Notes
5000	COGS - Category 1	Cost of primary category products sold
5010	COGS - Category 2	Cost of secondary category products sold
5020	COGS - Category 3	Cost of tertiary category products sold
5100	Repair Parts Cost	Cost of parts used in repairs

2.6 Expenses

Code	Account Name	Notes
6000	Cash Over / Short	Drawer variance — over is credit, short is debit
6100	Payment Processing Fees	Card processor transaction fees
6200	Bad Debt Expense	Written-off account balances
6300	Inventory Shrinkage	Inventory adjustments and write-offs

2.7 Revenue Category Mapping

Revenue and COGS accounts (4000-4020 and 5000-5020) map to product categories defined in the inventory module. Each business configures which product categories roll up to which revenue accounts. This mapping is stored in a category_account_mapping table.

For a music store, the defaults might be:

• 4000/5000 → Instruments
• 4010/5010 → Accessories
• 4020/5020 → Supplies (strings, reeds, books)

For a bike shop:

• 4000/5000 → Bicycles
• 4010/5010 → Parts & Components
• 4020/5020 → Apparel & Accessories

The account names and category mappings are fully configurable. Additional revenue/COGS account pairs can be created if a business needs more granularity.

3. Database Schema

3.1 account_code

Business-configurable chart of accounts. Each business maps platform account codes to their QuickBooks account names and numbers.

Column	Type	Notes
id	uuid PK
company_id	uuid FK
code	varchar(10)	e.g. "1000", "4010"
name	varchar(255)	Display name
account_type	enum	asset, liability, revenue, contra_revenue, cogs, expense
normal_balance	enum	debit, credit — derived from account_type, enforced
quickbooks_account_name	varchar(255)	Must match QB exactly for import
quickbooks_account_number	varchar(20)	Optional — QB account number
is_system	boolean	System accounts cannot be deleted
is_active	boolean	Inactive accounts cannot receive new entries
created_at	timestamptz
updated_at	timestamptz

Normal balance derivation:

• Assets, Expenses, COGS → debit
• Liabilities, Revenue, Contra Revenue → credit

3.2 journal_entry

Header record for each accounting event. One journal entry per financial event — groups all debit and credit lines for that event.

Column	Type	Notes
id	uuid PK
company_id	uuid FK
entry_number	varchar(20)	Auto-generated, e.g. JE-2026-00142
entry_date	date	Accounting date — may differ from created_at
period_id	uuid FK	References accounting_period — null if no periods defined
entry_type	varchar(50)	See section 4 for full list
source_entity_type	varchar(50)	transaction, rental, enrollment, repair, drawer_session, batch
source_entity_id	uuid	FK to the originating record
description	text	Human-readable description for accountant
total_debits	numeric(12,2)	Must equal total_credits
total_credits	numeric(12,2)	Must equal total_debits
export_batch_id	uuid FK	Set when entry is included in an export
exported_at	timestamptz	When exported — null if not yet exported
reconciled_at	timestamptz	When accountant confirmed import to QB
is_void	boolean	Voided entries excluded from exports
void_reason	text	Required if voided
voided_by	uuid FK	User who voided
voided_at	timestamptz	When voided
reversal_of_id	uuid FK	If this is a reversing entry, references the original
created_by	uuid FK	System or employee
created_at	timestamptz

Precision: numeric(12,2) supports values up to $9,999,999,999.99 per entry.

3.3 journal_entry_line

Individual debit and credit lines for each journal entry. Every entry must have at least one debit and one credit line and total_debits must equal total_credits.

Column	Type	Notes
id	uuid PK
journal_entry_id	uuid FK
account_code_id	uuid FK	Which account is affected
line_type	enum	debit, credit
amount	numeric(12,2)	Always positive — line_type determines direction
description	text	Line-level description
entity_type	varchar(50)	Optional — customer, vendor, employee for sub-ledger
entity_id	uuid	Optional — FK to account, supplier, etc.
created_at	timestamptz

3.4 accounting_period

Accounting periods for month-end close. Optional — if no periods are defined, entries can be posted to any date.

Column	Type	Notes
id	uuid PK
company_id	uuid FK
name	varchar(50)	e.g. "March 2026"
start_date	date	Period start (inclusive)
end_date	date	Period end (inclusive)
status	enum	open, closed, locked
closed_by	uuid FK	User who closed the period
closed_at	timestamptz
created_at	timestamptz

Period status:

• open — entries can be posted
• closed — no new entries without manager override (soft close for month-end review)
• locked — no new entries, period is final (after QB reconciliation)

Posting to a closed period requires accounting.admin permission. Posting to a locked period is blocked entirely.

3.5 export_batch

Records each export operation for audit and reconciliation tracking.

Column	Type	Notes
id	uuid PK
company_id	uuid FK
exported_by	uuid FK	User who initiated export
export_format	enum	csv, iif
date_range_from	date
date_range_to	date
entry_count	integer
total_amount	numeric(12,2)	Sum of all debit amounts in batch
file_path	varchar(500)	Storage path for export file
reconciled_at	timestamptz	When accountant confirmed import
reconciled_by	uuid FK
created_at	timestamptz

3.6 category_account_mapping

Maps product categories to revenue and COGS accounts.

Column	Type	Notes
id	uuid PK
company_id	uuid FK
category_id	uuid FK	References product category
revenue_account_id	uuid FK	References account_code
cogs_account_id	uuid FK	References account_code
created_at	timestamptz

3.7 tax_rate

Sales tax rates by jurisdiction. Supports multi-rate jurisdictions (state + county + city).

Column	Type	Notes
id	uuid PK
company_id	uuid FK
name	varchar(100)	e.g. "Texas State", "Travis County", "Austin City"
rate	numeric(6,4)	e.g. 0.0625 for 6.25%
jurisdiction	varchar(100)	e.g. "TX", "Travis County, TX"
is_active	boolean
sort_order	integer	Order applied (state first, then county, then city)
created_at	timestamptz
updated_at	timestamptz

Tax rates are applied at the location level — each location has a tax profile that combines applicable rates. The combined rate is calculated at the time of sale, and the total tax is posted to Sales Tax Payable (2000) as a single line item. The tax rate breakdown is stored on the transaction record for reporting.

4. Journal Entry Mappings

Every financial event generates one or more journal entries automatically. The following tables show the exact debit and credit mapping for each event type. All entries are generated by the platform — staff do not create journal entries manually.

Payment processor references below are generic — "Payment Clearing" (1200) applies to any processor (Stripe, Global Payments, or future providers). The clearing account is reconciled against processor payout reports.

4.1 Cash Sale

Debit	Credit	Notes
1000 Cash - Register Drawer	4000-4020 Sales Revenue	Revenue recognized at point of sale
1000 Cash - Register Drawer	2000 Sales Tax Payable	Tax collected from customer
5000-5020 COGS	1300 Inventory - Sale Stock	Cost of item removed from inventory

4.2 Card Sale

Debit	Credit	Notes
1200 Payment Clearing	4000-4020 Sales Revenue	Card payment in transit to bank
1200 Payment Clearing	2000 Sales Tax Payable	Tax collected
5000-5020 COGS	1300 Inventory - Sale Stock	Cost of item sold

When processor settles to bank account (triggered by payout webhook or manual reconciliation):

Debit	Credit	Notes
1000 Cash (Bank)	1200 Payment Clearing	Funds settled from processor to bank
6100 Payment Processing Fees	1200 Payment Clearing	Processor fee deducted from payout

4.3 Discount Applied at POS

Debit	Credit	Notes
4900 Sales Discounts	4000-4020 Sales Revenue	Contra revenue — keeps gross revenue clean

Note: Gross revenue is always recorded at full price. The discount is recorded separately as a contra-revenue debit. Net revenue = Sales Revenue minus Sales Discounts. This gives the accountant visibility into both gross and net figures.

4.4 Sale Refund

Debit	Credit	Notes
4910 Sales Returns & Refunds	1000/1200 Cash or Payment Clearing	Refund issued to customer
1300 Inventory - Sale Stock	5000-5020 COGS	Item returned to inventory at cost
2000 Sales Tax Payable	1000/1200 Cash or Payment Clearing	Tax refunded

4.5 Rental Payment Received

Standard month-to-month rental — full payment is earned revenue:

Debit	Credit	Notes
1200 Payment Clearing	4100 Rental Revenue	Monthly rental payment — earned immediately
1200 Payment Clearing	2000 Sales Tax Payable	Tax if applicable to rentals in jurisdiction

4.6 Rent-to-Own Payment Received

RTO payments split between earned rental revenue and deferred equity portion:

Debit	Credit	Notes
1200 Payment Clearing	4100 Rental Revenue	Rental portion — earned immediately
1200 Payment Clearing	2120 Deferred Revenue - RTO Equity	Equity portion — not earned until buyout

4.7 Rent-to-Own Buyout Completed

When customer exercises buyout option — deferred equity is recognized as revenue:

Debit	Credit	Notes
2120 Deferred Revenue - RTO Equity	4400 RTO Buyout Revenue	Accumulated equity recognized on buyout
1200/1000 Payment Clearing or Cash	4400 RTO Buyout Revenue	Remaining buyout balance collected
5000 COGS	1310 Inventory - Rental Fleet	Cost of item transferred from fleet to sold

4.8 Rental Security Deposit Collected

Deposit is a liability — not revenue until earned or applied:

Debit	Credit	Notes
1000/1200 Cash or Payment Clearing	2200 Rental Deposits Held	Deposit received — held as liability

4.9 Rental Deposit Returned

Debit	Credit	Notes
2200 Rental Deposits Held	1000/1200 Cash or Payment Clearing	Deposit refunded to customer on return

4.10 Rental Deposit Kept (Damage)

Debit	Credit	Notes
2200 Rental Deposits Held	4500 Other Income	Deposit applied to damage — now earned income

4.11 Lesson Payment Received

Debit	Credit	Notes
1200 Payment Clearing	4200 Lesson Revenue	Lesson payment — earned for current period

Revenue recognition note: If the business recognizes lesson revenue per session delivered rather than per billing period, the entry on payment would credit Deferred Revenue - Lessons (2110) and recognize revenue as each session is marked attended. Most small businesses bill monthly and recognize on billing — either approach is acceptable but must be consistent within a fiscal year. The business selects their method in settings.

4.12 Makeup Lesson Credit Issued

Debit	Credit	Notes
4200 Lesson Revenue	2300 Customer Credits	Revenue reversed for undelivered lesson

4.13 Repair Payment Collected at Pickup

Debit	Credit	Notes
1000/1200 Cash or Payment Clearing	4300 Repair Revenue - Labor	Labor charges collected
1000/1200 Cash or Payment Clearing	4310 Repair Revenue - Parts	Parts charges collected
1000/1200 Cash or Payment Clearing	2000 Sales Tax Payable	Tax on parts if applicable
5100 Repair Parts Cost	1320 Inventory - Parts & Supplies	Cost of parts consumed in repair

4.14 Repair Charged to Account

Debit	Credit	Notes
1100 Accounts Receivable	4300 Repair Revenue - Labor	Repair billed to account — not yet paid
1100 Accounts Receivable	4310 Repair Revenue - Parts	Parts billed to account
5100 Repair Parts Cost	1320 Inventory - Parts & Supplies	Cost of parts consumed

4.15 Account Payment Received

Debit	Credit	Notes
1000/1200 Cash or Payment Clearing	1100 Accounts Receivable	Payment applied to outstanding balance

4.16 Bad Debt Write-Off

Debit	Credit	Notes
6200 Bad Debt Expense	1100 Accounts Receivable	Uncollectible balance written off — requires manager approval

4.17 Billing Date Change — Proration Credit

Debit	Credit	Notes
4920 Proration Credits Issued	1100/1200 AR or Payment Clearing	Credit issued to customer for billing date shift

4.18 Billing Date Change — Proration Charge

Debit	Credit	Notes
1200 Payment Clearing	4100/4200 Rental or Lesson Revenue	Additional charge for extended billing period

4.19 Inventory Purchase (Receiving PO)

Debit	Credit	Notes
1300 Inventory - Sale Stock	2500 Accounts Payable	Merchandise received — owed to vendor
1310 Inventory - Rental Fleet	2500 Accounts Payable	Rental fleet items received

4.20 Vendor Payment

Debit	Credit	Notes
2500 Accounts Payable	1000/1200 Cash or Bank	Payment to vendor for purchase order

4.21 Gift Card Sold (Module)

Debit	Credit	Notes
1000/1200 Cash or Payment Clearing	2350 Gift Card Liability	Gift card sold — liability until redeemed

4.22 Gift Card Redeemed (Module)

Debit	Credit	Notes
2350 Gift Card Liability	4000-4020 Sales Revenue	Gift card applied to purchase — liability becomes revenue

If gift card only partially covers the sale, the remainder is a separate payment entry (cash or card).

4.23 Consignment Sale (Module)

Debit	Credit	Notes
1000/1200 Cash or Payment Clearing	2500 Accounts Payable	Consignor's portion — owed to the owner
1000/1200 Cash or Payment Clearing	4500 Other Income (Commission)	Store's commission on the sale
1000/1200 Cash or Payment Clearing	2000 Sales Tax Payable	Tax collected

Note: consignment inventory is not on the store's books (the store doesn't own it). No COGS entry. The store's revenue is only the commission.

4.24 Cash Drawer — Opening Float

Debit	Credit	Notes
1000 Cash - Register Drawer	1020 Cash - Safe	Float transferred from safe to drawer for shift

4.25 Cash Drawer — Closing Variance

If drawer is over (more cash than expected):

Debit	Credit	Notes
1000 Cash - Register Drawer	6000 Cash Over / Short	Overage — credit to over/short account

If drawer is short (less cash than expected):

Debit	Credit	Notes
6000 Cash Over / Short	1000 Cash - Register Drawer	Shortage — debit to over/short account

4.26 Cash Drop Mid-Shift

Debit	Credit	Notes
1020 Cash - Safe	1000 Cash - Register Drawer	Cash moved from drawer to secure location

4.27 Batch Repair Invoice

Batch repair invoices follow the same pattern as individual repair payments but reference the batch record:

Debit	Credit	Notes
1100 Accounts Receivable	4300 Repair Revenue - Labor	Batch labor billed to account
1100 Accounts Receivable	4310 Repair Revenue - Parts	Batch parts billed to account
5100 Repair Parts Cost	1320 Inventory - Parts & Supplies	Cost of all parts used across batch

4.28 Store Credit Issued (Return without Receipt)

Debit	Credit	Notes
4910 Sales Returns & Refunds	2300 Customer Credits	Store credit issued in lieu of cash refund

4.29 Store Credit Redeemed

Debit	Credit	Notes
2300 Customer Credits	4000-4020 Sales Revenue	Store credit applied to purchase

5. Journal Entry Validation

Every journal entry is validated before being written to the database. Validation failures block the originating financial event and alert staff.

• total_debits must equal total_credits — entries that do not balance are rejected
• Every line must reference a valid, active account_code
• Entry date cannot be in the future
• Entry date must fall within an open accounting period (if periods are configured)
• Posting to a closed period requires accounting.admin permission
• Posting to a locked period is blocked entirely
• Voided entries generate a reversing entry — equal and opposite lines — rather than being deleted
• Reversing entries reference the original entry ID via reversal_of_id for traceability
• All amounts must be positive — the line_type (debit/credit) determines direction
• A journal entry must have at least two lines (at least one debit and one credit)

6. QuickBooks Export

6.1 Export Format

Journal entries are exported as CSV in a format compatible with QuickBooks Desktop and QuickBooks Online import. Each row represents one journal entry line.

CSV Column	Source
Date	journal_entry.entry_date
Journal No	journal_entry.entry_number
Account	account_code.quickbooks_account_name — must match QB exactly
Debit	journal_entry_line.amount where line_type = debit
Credit	journal_entry_line.amount where line_type = credit
Description	journal_entry.description
Name	account.name where applicable — for AR/AP lines
Class	Optional — location name for multi-location QB setups

6.2 Export Workflow

1. Staff or accountant selects date range for export
2. System returns count of unexported entries in range for confirmation
3. Export generated as CSV and stored via file storage — download link provided
4. All included entries marked with export_batch_id and exported_at timestamp
5. Entries already exported are excluded from subsequent exports by default
6. Override option available to re-export a specific batch — requires manager approval
7. Accountant imports CSV into QuickBooks — confirms successful import in platform
8. Confirmed entries marked reconciled_at — visible in reconciliation report

6.3 Export Frequency Recommendation

Daily export is recommended for active businesses to keep QuickBooks current. Weekly export is acceptable for lower-volume businesses. Monthly export creates large import files and increases risk of errors going undetected. The platform supports any frequency — the accountant decides what works for their workflow.

7. Accounting Periods

Accounting periods provide month-end close discipline. They are optional — small businesses that don't need formal period management can skip this entirely and all entries are posted without period validation.

7.1 Period Lifecycle

1. Open — default state. Entries can be posted freely.
2. Closed — soft close for month-end review. New entries require accounting.admin override. Allows corrections before finalization.
3. Locked — hard close after QB reconciliation. No entries can be posted. Period is final.

7.2 Month-End Close Process

1. Accountant reviews all entries for the period in the platform
2. Runs trial balance report — verifies debits equal credits across all accounts
3. Closes the period (status → closed)
4. Exports entries to QuickBooks
5. Confirms QB import is clean
6. Locks the period (status → locked)

7.3 Auto-Period Generation

Periods can be auto-generated monthly. The system creates the next period when the current one is closed. Businesses that don't use periods have no periods created — the feature is entirely opt-in.

8. In-Platform Accounting Reports

These reports are generated from journal entry data within the platform and do not require QuickBooks. They give the business owner operational financial visibility without waiting for the accountant's monthly close.

Report	Description
Trial Balance	Debit/credit totals by account — must balance to zero
Revenue Summary	Revenue by category by period
Gross vs Net Revenue	Gross revenue, discounts, returns, net — shows discount impact
AR Aging	Outstanding account balances by age — current, 30, 60, 90+ days
AP Aging	Outstanding vendor balances by age
Deferred Revenue	RTO equity, lesson credits, deposits held — future obligations
Cash Flow Summary	Cash in vs out by period — drawer, card payments, deposits
Payment Clearing Reconciliation	Amounts in clearing vs expected payouts — flags missing settlements
Export Status	Entries exported vs pending export — reconciliation tracking
Cash Over / Short History	Drawer variance by shift, employee, and register
COGS vs Revenue	Gross margin by product category
Tax Collected	Sales tax collected by jurisdiction and period
Gift Card Liability	Outstanding gift card balances (module)

9. Business Rules

• Journal entries are generated automatically — staff never create entries manually
• Every financial event must produce a balanced journal entry before the event is committed
• Entries are append-only and immutable — corrections made via reversing entries only
• Voided entries generate equal and opposite reversing entries — never deleted
• Exported entries are not re-exported unless explicitly overridden with manager approval
• Chart of accounts is configurable per business — account names must match QuickBooks exactly
• Payment clearing account must be reconciled against processor payout reports regularly
• Deferred revenue accounts reviewed quarterly — amounts that should have been recognized are flagged
• Bad debt write-offs require manager approval and are logged in audit trail
• Revenue/COGS accounts map to product categories — configurable per business
• Tax rates are location-specific — each location has a tax profile with applicable rates
• Gift card and consignment entries only generated when those modules are active

10. Posting Service Interface

The posting service is the single entry point for all journal entry generation. Domain services (POS, rentals, lessons, repairs) call the posting service with a business event — they do not construct journal entries directly.

AccountingService.post(companyId, {
  type: 'cash_sale',           // event type — maps to journal entry template
  date: '2026-03-30',          // accounting date
  sourceEntityType: 'transaction',
  sourceEntityId: 'uuid',
  description: 'Sale #1234 — 3 items',
  lines: [                     // optional override — normally auto-generated from event type
    { accountCode: '1000', type: 'debit', amount: 107.50 },
    { accountCode: '4010', type: 'credit', amount: 99.99 },
    { accountCode: '2000', type: 'credit', amount: 7.51 },
  ],
  metadata: {                  // domain-specific context
    transactionId: 'uuid',
    customerId: 'uuid',
    items: [...],
  },
})

The posting service:

1. Resolves the event type to a journal entry template (or uses provided lines)
2. Looks up the correct revenue/COGS accounts from category mappings
3. Calculates tax from the location's tax profile
4. Validates the entry balances (debits == credits)
5. Validates the entry date falls in an open period
6. Writes the journal entry and lines in a single transaction
7. Returns the journal entry ID

If validation fails, the posting service throws and the originating event is rolled back. No financial event can be committed without a valid journal entry.

11. Implementation Order

1. account_code table + seed default chart of accounts
2. journal_entry + journal_entry_line tables
3. Posting service with validation (balance check, period check, account check)
4. tax_rate table + location tax profiles
5. category_account_mapping table
6. accounting_period table + open/close/lock endpoints
7. Journal entry list/detail API endpoints (read-only for staff)
8. Void + reversing entry flow
9. export_batch table + CSV export
10. In-platform reports (trial balance first, then others)
11. Integration hooks from POS, rentals, lessons, repairs (added as each domain goes live)
12. QuickBooks reconciliation workflow