198.263.  Increase in tax levy, procedure — ballot of submission, form. — Any district which has a lower tax levy than the maximum levy authorized by section 198.250 may increase its levy up to, but not in excess of, such maximum levy if a majority of the voters of the district who vote on the increase approve the increase.  The ballot of submission for a tax increase under this section shall be in substantially the following form:

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If a majority of the qualified voters casting votes thereon are in favor of the increase, the board of directors of the district shall levy the annual rate of tax approved; but if a majority of the voters casting votes thereon are opposed to the increase, any annual tax rate in effect at the time of the election shall remain in effect; provided, however, that if the voters of the district have previously approved a levy and the levy has not been imposed, the board of directors may impose such previously approved levy or portion thereof, subject to other provisions of the law with respect to limitation on tax revenues.