Hi,
In very old version it was possible to apply the payment with a postign date before the posting of the invoice, but this has been blocked in order to prevent a data mess.
The point was that on applying entries with currency adjustments or with payment discount/ payment tolerances and the "adjust VAT for Paym. disc." feature enabled some of the detailed customer/vendor ledger entries for the payment got the posting date of the later invoice and some got the posting date of the payment. On running reports which used the detailed entries (Balance at Date, Detailed Trial Balanceetc) you got differences when you compared the totals with the total s of the G/L Trial Balance.
With the "adjust VAT for Paym. disc." feature enabled you also got VAT Entries with different posting dates compared to detailed customer/vendor ledger entries
Therefore "direct application" and also the manual application (afterwards, when invoice and payment have been posted but not applied yet) check for the dates and can only be posted with a posting date at or later than the later date.
If you want to take the check out of the code ... you can do that on an individual base ... but you can end up with the described data mess, if you use currencies or the "adjust VAT for Paym. disc." feature.
This change (taking out the check) is not supported by Microsoft.
Hope this answers
