The most common trigger is a bank mandate: opening an account, changing authorised signatories, or setting the threshold above which two signatures are required. Banks will not act on an informal instruction. They want a resolution naming the account, the signatories and the limits, certified by the secretary or a director. The next most frequent use is an appointment, whether of a director, a company secretary, a treasurer or an authorised representative, where the resolution is the document ACRA filings and third parties rely on to confirm the person's authority.
Approving a contract or transaction is the third recurring scenario. A resolution authorising the organisation to enter a lease, a loan facility, a service agreement or a major purchase gives the counterparty comfort that the signatory is acting with proper authority, and it protects the directors by showing the decision was taken collectively. Closely related is the grant of delegated authority, where the board empowers a named officer or sub-committee to act up to a defined limit, so day-to-day matters do not need a fresh resolution each time.
Two edge cases are worth flagging. First, a resolution approving a related-party transaction must record the interested director's disclosure under section 156 and, depending on the constitution, that director may need to abstain. Second, where directors are spread across time zones, a written resolution in counterparts is often the only practical route, and the date the resolution takes effect is the date the last required signature is given, not the date it was circulated. Get that wrong and a bank may reject the mandate.