You can deduct the monthly payments (for the year in review) before calculating the amount of Zakah. However, you are not allowed to deduct the entire mortgage. If we do so, then no one would be  paying zakah as most people have mortgages  for homes or businesses. So, you are allowed only If the jewelry is for personal use you don't need to pay Zakah on it unless it is considered as excessive or extravagant.   For details, please refer to the following answer.

• My mother has some gold jewellery. Every year she used to give zakaat but this year my dad's financial condition is very bad and is in deep debt. Is it okay if we don't give out zakaat this year and ask for forgiveness in not being able to do so? Please give some suggestions. We heard from someone that if one is in deep financial crisis zakaat can be overlooked is that true?