As stated in “Forms of bail”, bail conditions may include a person being released upon entering into an undertaking with a surety or sureties or a deposit (s 5(2)(c) Bail Act).
A surety is another person who is bound to ensure that the accused surrenders themselves into custody in accordance with the conditions of bail. The surety may be required to pay the amount set for the bail if the accused fails to attend the court in accordance with the undertaking. The surety may also have to put down a deposit of money or other security (e.g. property) to enable the accused to be released on bail.
See the comments of Justice Gillard in R v Mokbel & Mokbel  VSC 158 and Mokbel v Director of Public Prosecutions (Vic) & Director of Public Prosecutions (Cth)  VSC 487 in relation to the appropriateness of a person as a surety, whether the surety has taken adequate steps to ensure an accused answered their bail and the penalties to which a surety is liable.
Any person over the age of 18 years who is not under any legal disability (e.g. not a person of unsound mind), and who has money or assets not less than the value of the bail, may be a surety. This does not include a corporation or other association.
The bail decision-maker has a discretion as to whether to accept a person as a surety (s 9).
Matters taken into account to determine whether a person is a suitable surety include:
• the financial resources of the proposed surety;
• the character and prior convictions of the proposed surety;
• the proximity (by reason of kinship, residence or other relationship) between the accused and the proposed surety (presumably, the closer the proximity, the greater will be the opportunities for the surety to exercise control over the accused and an accused’s willingness to abide by any bail order).
Before admitting a person to bail with a surety, the bail decision-maker must be satisfied of the means of the surety. This will be done by asking on oath any questions thought necessary, and by requiring the proposed surety to sign an affidavit.
A surety may appear at court or give information and undertakings via an audiovisual link (s 9(3A)).
When a person has been admitted to bail with a surety, the obligations of the surety continue until:
• the death of the surety (s 20);
• the accused appears at court in accordance with the undertaking;
• if the accused appears at court in accordance with the undertaking and the matter is postponed or adjourned, until the accused again appears at court in accordance with the extended undertaking for bail (except where the surety elects at the initial granting of bail not to be liable on any extension of bail without further consent) (s 16);
• the surety applies to the police or court that granted the bail for a discharge of liability (this application may be made by a surety at any time); in such cases, the accused is brought before the court and has to find another surety if they are to be released again on bail (s 23);
• the accused is remanded in custody pending hearing of the charge (s 19).
If the accused fails to appear at court in accordance with the bail conditions, the surety is liable to forfeit their deposit or they become indebted to the Crown for the deposit amount. However, a surety has rights under the Crown Proceedings Act 1958 (Vic) (s 6) to apply for an order varying or rescinding the forfeiture.
It is an offence for a person to indemnify (i.e. guarantee) a surety, or to indemnify any liability that the surety might incur arising from their surety obligations. The other person and the surety may be guilty of this offence, which carries a fine of 15 penalty units or three months imprisonment (s 31 Bail Act).