👉 Invoice math refers to the process of calculating the total amount due based on various components like subtotal, tax, discounts, and shipping fees. It starts with the subtotal, which is the base amount for the invoice. Tax is then added as a percentage of the subtotal, calculated using a predefined tax rate. Discounts, if any, are subtracted from the total, and shipping fees, if applicable, are added. The formula typically looks like this: Total = Subtotal + (Subtotal
Tax Rate) - Discounts - Shipping Fees. This ensures that the invoice reflects all applicable charges accurately before finalizing the amount due.