Question Summary:
I did not have access to my father’s inheritance for 7 years. How do I calculate Zakat for those years?

Question Detail:

I have a query relating to zakaat.
My Father had passed away 7 years ago and had left me jewellery and an investment policy.
I had no access to the jewellery nor did I have a value of the policy due to legal issues.
Recently I have come to know the  weight of the jewellery and the value of the investment.
How do I go about calculating the zakaat owed for these years ? Do I use historic gold prices to calculate the zakaat and do I use the tax year-end value of the investment for each prior period or do I calculate the zakaat on todays value of the gold and investment and pay it as 1 amount multiplied by the number of years which has passed?

Answer :

In the Name of Allah, the Most Gracious, the Most Merciful.
As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh.
An inheritance that one does not have access to is defined as a weak debt. The ruling on weak debts such as inheritance is that there is no Zakat due on it for those previous years when one did not have any access to it. [i][ii][iii][iv]
→ If you were already sahib al-nisab (i.e. Zakat was obligatory on you) before you got access to this inheritance, then this inheritance will be considered a part of your total wealth in the year you got access to it and you will calculate Zakat on it just as you do on the rest of your wealth. 
Example: If you got access to your inheritance this year and your annual Zakat date is sometime next month, then your inheritance will form part of your zakatable wealth on that date.
→ If you were not sahib al-nisab before receiving this inheritance, and this inheritance (either by itself or added to whatever wealth you had from before) reaches the amount of nisab (612.35 grams of silver), then you will wait one lunar year from the date you got access to this inheritance. At the expiry of one lunar year from that date you will calculate your Zakat (if you still possess the amount of nisab) and this date will be your annual Zakat date going forward.
And Allah Ta’āla Knows Best
Sohail ibn Arif,
Student Darul Iftaa
Chicago, USA
Checked and Approved by,
Mufti Ebrahim Desai.
 
وأما الدين الضعيف فهو الذي وجب له بدلا عن شيء سواء وجب له بغير صنعه كالميراث، أو بصنعه كما لوصية [i]
 أو وجب بدلا عما ليس بمال كالمهر، وبدل الخلع، والصلح عن القصاص، وبدل الكتابة ولا زكاة فيه ما لم يقبض كله ويحول عليه الحول بعد القبض.
  بدائع الصنائع، ٢/ ١٠
و) عند قبض (مائتين مع حولان الحول بعده) أي بعد القبض (من) دين ضعيف وهو (بدل غير مال) كمهر) [ii]
 ودية وبدل كتابة وخلع، إلا إذا كان عنده ما يضم إلى الدين الضعيف
 الدر المختار، ٢/ ٣٠٦
فتاوى دار العلوم ديوبند، ٢/ ٥٦ [iii]
فتاوى محمودية، ٩/ ٣٧٧ فاروقية [iv]