Absences from the UK during the Residential Qualifying Period (British Citizenship- Naturalisation)
There are various requirements for obtaining British naturalisation. Applicants must be a minimum of 18 years of age, of sound mind, able to communicate adequately in English, Welsh or in Scottish Gaelic and possess good character. The residential requirements are:

Be a resident of the UK for a minimum of three years before the date of filing an application
Must not have remained outside the UK for more than 270 days during those three years
Must not have spent more than 90 days outside the UK in the last year before applying
Not have breached any immigration rules during the three years

All conditions must be fulfilled in order to obtain Naturalisation.
Non-fulfilment of any condition often leads to rejection of the application.
However, in some circumstances, some exceptions may be made with regards to the absence time period.