Cash purchases above rs.20000/-

Respected Sir,

We have to purchase diesel at various sites. Not a single petrol pump can given the diesel on Credit basis we have to purchase the diesel through cash only.If we purchased diesel for Rs. 45000/- through cash whether single voucher to be prepared for Rs. 45000/- or three vouchers to be prepared of Rs.18000/-,Rs.18000/-  and Rs.9000/- for different dates and then accounted ?

Kindly advice for the same.

Regards