Tier 2 vis Extension within UK while spouse now granted ILR

Hi,
I think it is best to post this question separately to get clear response.
The spouse was on Tier 2 when the initial application was made outside of UK for partner as dependant. Tier 2 was valid for one year for the spouse (on 4th year of Tier 2). Hence dependent was issued 1 year Tier 2 dependent visa which is now coming to end. Spouse applied for ILR recently after completing 5 years continuous stay and has been granted ILR status. Dependent has to now apply for visa extension. Should the extension be made under ILR dependent or from the last visa issued which was Tier 2. The application states to provide details of last visa issued even if ILR or citizenship was issued. After submitting the dependent visa application, when took to IHS payment webpage, it stated some information are missing and the application is asking for start and end work date of the spouse! But as spouse is now given ILR status, hence there is no end date to his work and job is permanent position. What date should be provided in the work end date?
Can anyone help them it’s urgent!
Thanks!