"(checks have been lost)."

But you issued them, so delete is not proper. Void also changes your financial reports, and you did incur those costs. This is a Banking issue, not backing out Expense.

If you intend to reissue them, the make a deposit with the current date for the total, posting to an Other Liability account. Make replacement checks in the current date and pay out that liability.

The deposit for the total, and the uncashed checks, all clear against each other the next reconciliation to net of 0. The new checks will then clear, and this is not new expense.