Switch visa category from T2 ICT(Primary), T2 ICT Staff dependant to T2 General Dependants

Dear Advisors & Experts,

Appreciate your help and advise on switching my family members current visa to T2 General dependancy and IHS(immigration health surcharge).

I am in the UK on T2 General visa.
My wife and son with me on T2 ICT, wife as primary and son dependent.

Planning to switch their visa to T2 General dependant within the UK.

1. Can this shift feasible without leaving the country?

2. While calculating their IHS fee in the provided calculator, bit confused on which option to choose, Applying alone (or) Applying to join somebody (a main applicant) in the UK.

3. Applying alone gives the option to choose the required visa category and IHS gets calculated for the chosen type - in our case T2 PBS dependant up to 3 years, hence calculates for 3 years

4. Choosing the other option as "Applying to join somebody (a main applicant) in the UK" has an additional section to input as About the person you are joining in the UK providing my visa end date calculates the IHS considering my leftover years which is 4.5 years(i.e 4.5 years left on my T2 General)

5. Will their dependant visa period be based on my leftover years (or) can we opt for 3 years as required.

6. As she already on T2 ICT, has she to provide any employer letters along with the application to do the switch?

Thanks in advance.
D

1. Can this shift feasible without leaving the country? - YES POSSIBLE

2. While calculating their IHS fee in the provided calculator, bit confused on which option to choose, Applying alone (or) Applying to join somebody (a main applicant) in the UK. - Applying to join somebody

3. Applying alone gives the option to choose the required visa category and IHS gets calculated for the chosen type - in our case T2 PBS dependant up to 3 years, hence calculates for 3 years

4. Choosing the other option as "Applying to join somebody (a main applicant) in the UK" has an additional section to input as About the person you are joining in the UK providing my visa end date calculates the IHS considering my leftover years which is 4.5 years(i.e 4.5 years left on my T2 General) - This is correct.

5. Will their dependant visa period be based on my leftover years (or) can we opt for 3 years as required. - NO I dont think so. It will be based on main applicants end date Extensions for dependent happens in blocks of 3 years.

6. As she already on T2 ICT, has she to provide any employer letters along with the application to do the switch? - Either resignation letter or no objection from current employer would help. Never came across this scenario. She cant switch without informing current employer.