Hoe to manage utility payment in erpnext accounting when there is VAT?

For utility payment like purchase using petty cash,we will directly use journal entry for entering payment details.

but when there is vat how can i add this type of purchase without using purchase invoice,because vat details available in purchase invoice only

it is very difficult to use purchase invoice for small purchases because lot of suppliers we need to add for enter utility purchase details in purchase invoice,it is time consuming.