Your accounting date is also known as your accounting reference date or year end date
It is the date up to which your accounts are prepared and is generally the end of a calendar month. For example 31 December or 31 March.
Depending on your business type the year end can be set by you or it could have been already set up.
The year end of the limited company will have been allocated on set up of the company by Companies House.
The year end will be the end of the month in which the company was set up. For example if the company was set up on 5 March 2009 then the year end will be 31 March and the first accounts will be due at 31 March 2010.
HMRC will not know this date as Companies House and HMRC do not work together!
So you also have to inform HMRC of the year end date. This is done on a form called a CT41 G which will be sent from HMRC to the registered office address of the limited company shortly after it has been set up.
The year end date can be changed but this has to be communicated to Companies House on a special form and also to HMRC.
You will find that it is likely that the company has a different year end to the tax year end which is 5 April. This is fine but there are deadlines for both the company year end and the tax year end.
Your accountant should advise on these.
As regards filing your accounts then the following are important:
You can select an accounting date and you will let HMRC know what this date is when you fill in your self assessment forms.
Often you will find that businesses select the 5 April as this is the end of the tax year.
If you do want to use a date other than 5 April then this is something you should discuss with an accountant as you could start to delve into an area called overlap relief! (sorry for the bit of accounting talk there)