Hi Sudhakar,
if what Marssel suggested doesn't help either and you need to trace down the error without reproduction possibilities, here's what I would do:
First find out where the message 'G/L account xxxxxx in tax code XX not found' originates from, i.e.: If you got a message Number in the job log as well, go to SE91 and do a where-used on the message to get the points in the coding for a debugging approach. If there is no message number in the log, first search via SE11 Table T100 for Text with a string that is like the error message you get, for example "*G/L account*tax*". Then look whether you find your message here. If you do, go to SE91 again and do a where-used with the respective message number. If not, the message most likely originates from the local frame program; look there whether you can find the message string in the text-symbols, in constants or even in literals. If you find a respective text-symbol, do a where-used again etc. I think you got a grip 
Bottom line you will find out the points in the code where the message is supposedly thrown due to a certain condition. Once knowing the condition you can further narrow down the root cause.
Cheers, Lukas