If you run your business from your registered office in the UK :
Accounts must be sent to Companies House. The account reference date depends on when your Company was registered.
i.e : Company incorporated 05/08/99 > account reference date 31/08/00 (this date can be changed by filling in form 225 which Companies House sends to you nine months after your incorporation) > to be filed by 05/06/01 which is one year and ten months after the date of incorporation.
A penalty ranging from £100 to £1000 will be incurred for all accounts that are returned late.
If you have a turnover of more than £350.000 your accounts will have to be audited. Income Tax will be calculated on your net profits and depend on your Tax band.
If you have a turnover of more than £54.000 you must also register for VAT. A VAT number can be obtained via an accountant.