Its difficult to give you an answer when you haven't said which software it is that you're using. They often act differently.
For example, if its QuickBooks (the only one that I have experience of) it is easy for you to change the year end date in Company Settings, however, as the software doesn't 'roll over' until the end of that day (31st March for example) you can get a distorted retained earnings figure on 31st March compared to 1st April.
The best way, I find, to get over this is to do the following: assuming 31st March is year end.....
On the first day of the new financial year, check the general ledger and 'temporarily move' all 1st April transactions to 2nd April. Next double check the P&L by dating it from and to 1st April of the new financial year. It should read £0.00 of all transactions.
Now run the trial balance with a from and to date of 1st April again. The figures now will represent the same 'opening balance' figures that your accountant may have given you.
I hope this makes sense if it's QuckBooks that you're using.