My client is CA resident and owns a rental home in Arizona. He has to pay double tax, one to CA and other to AZ. Is he allowed to use Form 309 ( Credit for Taxes paid to Another State) ?

I am confused regarding this credit because IRS allowes tax paid in another State to be claimed on Form 1040.

I tried to fill the 309 form and it gives the Credit to a certain extent.

Thank you in advance for any help.