Each account has one main type from 13 fixed: cash, receivable, payable, inventory, prepayments, fixed assets, accumulated depreciation, accruals, other liabilities, unearned revenue, owner equity, revenue, expense. The type decides report place and behavior.

Signs: stored debit-positive. Assets and expenses are debit. Liabilities, equity, revenue are credit-negative, shown flipped. Each document balances to zero.

Customers and vendors are real accounts: each receivable names one customer, each payable one vendor. No generic buckets.

Each book starts with seven locked role accounts: main bank (cash), owner equity, accumulated depreciation, prepayments, unearned revenue, depreciation expense, and misc. Main bank is shown on the Balance form; the rest are hidden. Locked means cannot delete. Logic uses types and ids, never names, so renaming Rent changes nothing.