I struggled for hours with form CT600 (short) - the Company Tax Return and Accounts Service computational pdf form not letting me past the "Profit and loss" account.
It would show the error "X Error: The retained profit at XXXX-XX-XX must tally with the value in the balance sheet. Please check and amend your entries."
After checking and double-checking my figures to no avail, I found the fix was ANNOYINGLY simple!
Fill out the form normally, and get as far as the section PRIOR to "Profit and Loss account". This should be "Called up share capital".
Then, SAVE and CLOSE the pdf file.
Reopen the file - it will open where you left off - and press Next to enter the Profit and Loss account section. Be sure to put a 0 in the "Reserves" box if this was the case (you normally leave 0 boxes blank, but not here!).
Put in your figures; after entering the figure in the last box be sure to click somewhere else on the form so that box is saved.
Then, SAVE and CLOSE the pdf file again.
Reopen the file, press Next... and it should continue to the next section.
Of course, if that doesn't fix it... you may actually have an error with your amounts!
In which case, this may be of use: Guidance for common errors when completing the HM Revenue & Customs (HMRC) accounts template