The superintendent of public instruction shall recover (take back) state pupil transportation allocations that are not expended for the allowable student transportation program costs under the accounting guidance provided by the superintendent. The amount of the recovery shall be calculated as follows:

(1) Determine the district's state allocation for student transportation operations for the school year.

(2) Determine the district's allowable student transportation costs as follows:

(a) Sum the following amounts:

(i) The district's direct expenditures for general fund program 99 pupil transportation, and for educational service district student transportation operations expenditures in program 70 transportation excluding expenditures associated with the regional coordinator and bus driver training grants;

(ii) Allowable indirect charges equal to the expenditures as calculated pursuant to (a)(i) of this subsection times the state recovery rate as calculated in the district annual financial report;

(b) Subtract the district's revenues for the school year for revenue account 7199 (transportation revenues from other districts).

(3) If the allowable program costs are less than the state allocation, OSPI shall recover the difference.

(4) Special rule for the 2019-20 school year only. School districts may carry over state pupil transportation allocations that were not expended for allowable student transportation program costs from the 2018-19 school year to the 2019-20 school year.

Funds transferred into the transportation vehicle fund shall not be included as allowable transportation program costs for recovery calculations.