Budget of Expenses

I have a budget of my company. The budget is on monthly basis. This monthly budget amount are not transferable for next month. for example if I have budget for each month for rs. 700/- then it will laps after the month ends and not carried forward.

My question is if expenditure made in July month (bill date is in July) and due to non receipt of bill accounting made in August 2008.

Budget of which month is attracted July or August and why ?

Please advice

Thanks