Hi Gerita

I assume you are trying to post General journal entry here to Account's payable (AP), where in Sage 50 CA, AP is a linked account (Setup, settings, Payable/Purchases, Linked accounts)  

in order to post to link account, you need an Accountant's edition or you would have to un-link it in order to do so; however, if you use foreign currency on AP you shouldn't un-link it as it will reset your foreign values, if your data integrity is OK on Payable (you can check in Maintenance, Check data integrity) you shouldn't un-link it as it will cause data integrity issues.

Also Sage only allows you post to Current Fiscal and Last Fiscal year dates (2 year)

hope this helps

You could record the entry from the invoice screen.  Ask your accountant who the $250 is due to (I expect, to your accountant), and whether they intended for you to make the entry at all.

Your accountant may not have realized that your Accounts Payable is linked, and that prior years to 2017 are probably locked.

That is what I ended up doing. Thanks!