Invoices are crucial for several reasons: 1. Record Keeping: They provide a detailed record of business transactions, which is essential for accounting and auditing. 2. Legal Protection: Invoices serve as legal proof of the sale and can be used to resolve disputes. 3. Cash Flow Management: They help businesses keep track of money owed and manage their cash flow. 4. Tax Purposes: Invoices are necessary for calculating the amount of tax owed and for claiming tax deductions.