Visitor Visa - Stayed longer than mentioned during previous visit

[coolwind]

Hi,

I am in the process of applying for a visitor visa for my mother-in-law.

She has visited UK previously. In her previous she stayed in UK for 4 months but in
the form we had mentioned that would stay for around 2 months.

I am thinking of providing a cover letter in her application explaining why her previous visit was longer than expected ?
Has anyone been in similar situation before ?
What additional information and documentation would be required to justify the additional period of stay during the previous visit ?

[Casa]

What was the reason your mother extended her stay? The visa application would have been assessed on the statement she made regarding the intended length of the visit and staying in excess of this may have an adverse affect on future visitor visa applications.

[coolwind]

There was no specific reason for extending the stay. The visa was granted for six months so we assumed that the stay could be extended as long as it is within the validity period.

But, it seems this can be an issue for subsequent applications. We will ensure this time that the actual stay is same as that mentioned on the form. Is there any other information we can provide so that the home office is convinced?