If you live in a shared ownership property then your housing costs have a number of elements: a rental element, a mortgage/loan element and (in most cases) service charges. You can use the calculator to work out your entitlement to help with housing costs but beware - it is complicated!
You can claim help with the interest on your mortgage or loan through Pension Credit, Income Support, income-based Jobseeker's Allowance, income-related Employment and Support Allowance or Universal Credit. Housing Benefit or Universal Credit can pay for the rental element in the same way as for fully rented tenancies, and you may also be able to claim for eligible service charges.
To work out your entitlement you should first select "mortgage or owned outright", enter your mortgage costs (you can only get help with interest and from april 2018 it will be in the form of a Support for Mortgage Interest loan), and then see if you can get Pension Credit, Income Support, income-based Jobseeker's Allowance, income-related Employment and Support Allowance or Universal Credit which qualifies you for a SMI loan. Note that the DWP calculates your mortgage costs on a set interest rate figure which may be different from the interest you are paying. If the interest you pay is higher you will not receive help with all the costs.
You might also be eligible for Housing Benefit to help with your rent and/or service charge, whether or not you are eligible for mortage costs. So check your eligibility for these even if you are not able to get help with your mortgage/loan because of not being entitled to Pension Credit, Income Support, income-based Jobseeker's Allowance or income-related Employment and Support Allowance. Select "council or housing association tenant", enter your rent and then see if you can get Housing Benefit or Universal Credit Housing element.
In general, the same eligibility rules for service charges apply in all benefits: Housing Benefit, Pension Credit, Income Support, income-based Jobseeker's Allowance, income-related Employment and Support Allowance and Universal Credit. For information on what you can claim for see service charges. But note that you cannot claim for service charges for certain major repairs and improvements- instead you might get help with a loan taken out to cover them.