All appropriations shall lapse at the end of the fiscal year: PROVIDED, That the appropriation accounts may remain open for a period of thirty days, and may, at the auditor's discretion, remain open for a period not to exceed sixty days thereafter for the payment of claims incurred against such appropriations prior to the close of the fiscal year.

After such period has expired all appropriations shall become null and void and any claim presented thereafter against any such appropriation shall be provided for in the next ensuing budget: PROVIDED, That this shall not prevent payments upon uncompleted improvements in progress at the close of the fiscal year.