Which of the following is an advantage of paying bills by direct debit?

Paying bills by direct debit offers significant monthly budgeting assistance. This is because direct debits allow for automatic deductions from your bank account on set dates. By knowing exactly when payments will occur and how much is being deducted, individuals can manage their cash flow effectively. This consistency helps in planning monthly expenses, ensuring that essential bills are paid on time, and reducing the risk of late fees or missed payments.

The other options do not apply as they either relate to features not inherent to the direct debit process or do not support the specific context of bill payments. For instance, while flexible payment options might seem appealing, direct debits have a fixed schedule, which may not allow for changes in payment amounts or dates. Automatic savings account setup and guaranteed returns on investments pertain to entirely different financial mechanisms and do not relate directly to the advantages of paying bills through direct debit.