There is the setup guide on the Setup menu but it is just as easy to enter the outstanding invoices on the Historical tab of the customer/vendor.  So open the customer ledger or enter a new customer, then go to the Historical tab.  If you have just entered the customer name and other info, you will be forced to save the customer.

Then enter any outstanding invoice the customer owes as of the date you start to use Sage 50.  If there is an invoice with a partial payment, you can enter the invoice in full, then the payment.

Once you enter all information for all customers, use the Maintenance, Check Data Integrity option to make sure the amounts you entered balance with the amount you entered on the balance sheet account 1200 matches.  It must be the same.  You can run the Customer Aged report in Detail to make sure you entered everything under each customer correctly.

Then go back and repeat everything above an switch the word customer with vendor and 1200 to 2100 for all the vendor invoices owing.

You indicated that you have upgraded to Sage 50 2015, from what? If it was another Sage 50 version (older) then you do not have to re-enter the trial balance all that is required is to open the old data file and it will upgrade to match the program. Or restore from the last backup of the old program if it is Sage 50.

Thanks Alwyn, I missed the upgrade part.

Thanks for the suggestions. Turns out my accountant upgraded their system so I am not able to import their file with the year end adjustments and they cannot produce a paper copy of the adjustments so I can just make them myself.

They suggested I start a new company in Sage and enter the trial balances and that is where I have hit the stopping block. I must not have started the new company properly though as previous balances exist under my various ap and ar accounts. Should I start over again?