The whole point of the accrual system is to match income with expenses. A lot of vendors will use an invoice date that is in a period before or after the actual period the expense should be recorded.
Utilities are worse and usually use the generation date as the invoice date which is usually after the period of the service.

On the vendor bill screen, a simple "Accrue" checkbox with the corresponding "month to post" should suffice. The bill will then be debited against the expense just like any other bill but the user will have the option to accrue this bill to the proper period in the Manual Journal Section. The manual journal section could have a button that allows the user to accrue all of the invoices for a given month that have this "accrual" flag. A journal entry would then be automatically created that debits the expense and credits the designated "Accrued Liability" account. To offset the expense recorded when the invoice was posted, a corresponding reversal entry in the month the invoice was dated would automatically be created. This function should also mark the transactions that have been accrued so that they are not posted again if a second accrual batch is created.

This functionality should be able to handle the opposite possibility where vendor invoices are dated prior to the service month for services like rent, web hosting, etc. Instead the expense account would be credited and the designated "Vendor Prepayment" account would be debited in the period the invoice was posted. To record the expense, a corresponding reversal entry in the "month to post" would automatically be created.

This should be a major issue for most accountants as approximately 1% to 5% of all vendor transactions should require some type of accrual to match the expense with the corresponding revenue period. I hope this makes it to the top of your list as this functionality is critical for an accountant and would make our job much easier.