The government is examining a proposal to consider tweaks in GST (goods and services tax) rates only once a year against the present trend of periodic changes. Speaking at a press meet in Kolkata on Sunday, Union Finance Minister Nirmala Sitharaman said: “Periodically changing rates brings uncertainty and creates a ripple effect on businesses because they cannot ascertain how much to keep aside for the year. The government also does not know how much revenue would come in. So we, not formally, propose to the GST Council to consider a situation where rate rationalisation can be done only once a