in enterprise contractor edition of quickbooks, how can you allocate a journal entry to a job? for example expensing prepaid insurance

You can use the billable expense feature, dcap44.

The billable expense is an expense you incur on your customer’s behalf. You can easily record and track billable expenses so your customer/job can reimburse them when they receive their invoice. 

Let me show you how to set it up: 

1. Open your company file.
2. Click Edit and then Preferences.
3. From the left menu, click Time & Expenses.
4. Click Company Preferences.
5. Under Invoicing options, you can check the boxes to enable the feature.
6. Click OK.

Then, when you create a journal entry, you can select the job's name under the NAME column and check the Billable option. After you save the entry, you can invoice the expense. Here's how: 

1. From the Customers menu, click Create Invoices.
2. Select the job's name and you'll be prompted with the Billable Time Costs window.
3. Choose the Select the outstanding billable time and costs to add to this invoice and click OK.
4. Click the Expenses tab and select the item.
5. Select OK to add it to the invoice.

You can use this article to help you manage your jobs: Tracking job costs in QuickBooks Desktop.

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