No it makes no difference. All that will happen is you will get a message popping up saying something like the date is outside the financial year. I think from memory it says something like that. I have one accountant who doesn't like year end button pressed until after he has done all the journals etc.
As Amanda says no problem posting into the next year before you close down the current year. You normally need to keep it open for a while to ensure you have everything included. Before you close down and balance forward take a back up as this is the back up the accountant will want ie has everything included but before you balance forward.
As Amanda says if you post into the next year before you balance forward it will come up with an annoying message saying "posting outside of financial year"
Depending on the version of SAGE you can turn this off via; Settings/Company Preferences/Paramaters/Tick box "pause outside financial year message"
