経費の精算には、領収書の添付が必要です。

Excite翻訳: It is necessary to append the receipt for the adjustment of expenditure.
@nifty翻訳: Attachment of a receipt is required for settlement of accounts of cost.
Babel Fish: Attachment of territory acquisition is necessary in adjustment of expense.
Google翻訳: To pay the expenses, you must have a receipt attached.
Yahoo!翻訳: The attachment of the receipt is necessary for the adjustment of the expense.
OCN翻訳: Attachment on a receipt is necessary for adjustment of the expenses.
Windows Live Translator: Expense reimbursement requires receipt attached.

Summary:
Excite's has a natural sentence structure while Yahoo!'s "attach" seems to be better than "append" in Excite.
Windows's is very simple but expresses the intended idea.

Reverse Translation)
Excite翻訳: 費用の調整のための領収書を追加するのが必要です。
@nifty翻訳: 受取の付属はコストのアカウントの解決に必要です。
Babel Fish: 領域の獲得の付属品は費用の調節で必要である。
Google翻訳: 費用を支払うためには、領収書を添付する必要があります。
Yahoo!翻訳: レシートの付属品は、出費の調整のために必要です。
OCN翻訳: 受け取りのアタッチメントは経費の調整に必要です。
Windows Live Translator: 経費払戻しが添付入庫を必要です。

Summary:
Google's can be OK depending on the situation though it appears that the subject in the main clause is not consistent with that in the infinitive phrase.