The federal government may be forced to increase the rate of the major bank levy next year in order to meet its revenue forecasts. The Morrison Government is expecting revenue collected through the major bank levy to swell over the next three years, despite the Sydney property price correction and a slowdown in mortgage lending.Estimates published on Monday in the Mid-Year Financial and Economic Outlook show that the government believes it is in line to grow bank levy revenue by at least 6 per cent a year over the next four years.The government raked in A$1.13 billion from the levy in the 12 months to the end of June, but sees the take climbing to $1.55 billion in the current year and to $1.85 billion in 2022.Given flagging clearance rates in Melbourne and Sydney, it is difficult to fathom how prevailing market conditions are likely to support the projected increases in levy revenue.The levy, which is collected at the end of each quarter from the major banks, is calculated at 0.015 per cent of the wholesale funding liabilities sitting on their balance sheets.For the government to grow its cash take from the levy in line with its forecasts, the banks will have to boost their wholesale funding activity progressively over the next three years. However, the slide in property prices and weakening dwelling investment are more likely to dampen their wholesale funding requirements.That, in turn, would likely constrain revenue raised through the levy.Under such as scenario, the government would have to increase the rate at which it applies the levy to meet its budget forecasts.