After you have lived in the UK for a continuous period of 5 years, you can apply for confirmation of your permanent residence. You must have been in employment, in self-employment, studying or self-sufficient in the UK throughout the 5-year period.
For your residence in the UK to be considered continuous, you should not be absent from the UK for more than 6 months each year. However, longer absences for compulsory military service will not affect your residence. Additionally, A SINGLE ABSENCE OF UP TO 12 MONTHS FOR IMPORTANT REASON SUCH AS MINE (SERIOUS ILLNESS) WILL NOT AFFECT MY RESIDENCE WHEN APPLYING FOR Permanent RESIDENCE?