Bill
You need to be entitled to Income Related ESA in order to receive SMI, this will dependant on your household income, your savings and assets, and any hours that your partner works. See
Asset rule for ESA(IR) 24 hour work rule for ESA(IR) If you believe that you are then you should contact the DWP for an ESA3 form which captures your financial details and allows then to make a Decision on your eligibility for ESA(IR), phone the DWP office dealing with your claim for the form.
Gordon