An instrument which allows public officers to increase expenditure within a year is

A supplementary budget is an instrument that allows public officers to increase expenditure within a year. It is used when the original budget is not enough to cover all the necessary expenses, and more funds are needed to meet the demands of a particular situation or project. A supplementary budget is a document that outlines the additional funds needed and the reasons for the increase. This document is then presented to the relevant authorities for approval, allowing for the adjustment of the budget accordingly. This process ensures that the public sector can operate effectively and efficiently, with the necessary resources available to carry out their duties.