Standar Visitor Visa - Multiple Entry - Rules

[Magus1984]

Hi there,
I am a British Citizen (by Naturalisation). Over the last 5 years my non-uk parents have visited the UK a couple of times using a tourist visa. They have applied each time for a single entry visa.

I am having a baby and I would like my parents to come more regularly so I am thinking on applying to the 5year standard visitor visa for them.

I was wondering where I can find guidance about the rules of this visa? I understand that they could stay for a maximum of 6 months on each visit. But is this 6 months per calendar year?

Thanks,
M

[CR001]

6 months in any 12 months period. They cannot be spending more time in the UK than they do in their home country in any 12 month period.

[secret.simon]

Also see this thread.

The two rules to remember are
(a) Each single visit cannot exceed 180 days, and,
(b) Residing in the UK in the guise of "frequent and successive visits" is not allowed and the Immigration Officer at the airport can cancel the visa at the airport and deport the visitors if, in their view, the visitors are trying to reside in the UK using a long term visit visa.