Need help with Balance sheet out of balance

SUGGESTED

Our books were in balance as of  12/31/18 when closed.  As of the end of 2019 they are out of balance.  It appears the problem is in 2018 which means we need a one sided entry to 2018, which is closed and appears to be impossible to go back.  Does anyone have fix that would not require going back to that and then having to reenter all information?