Hello SFA,
Is this an expense related invoice?
If it is and you want to have that expense included in the previous month you would have to post a correction invoice to cancel the expense that is recorded in the current month and post another invoice transaction in the previous month. This requires that you re-open the previous period. Re-opening the period and posting an additional expense has implications on your month end reporting and before you are doing that I would recommend talking with the finance manager if he/she really wants to have that.
In case of an invoice that is not expenses, I would like to know why you want to post this invoice into the previous month?
If it does not affect your expenses and therefore the P&L, you would only show a 'longer' Balance Sheet that includes an additional amount on the assets and liabilities side.
Not sure whether this is really necessary from a financial standpoint.
Best regards,
Ludwig