Zakaat

Discharging one's zakaat on valuations given of investments

Q: My official zakaat payment date is in Rajab. However, many Islamic investment companies/groups (whether small or big) provide the zakaat valuation/calculation during Ramadhaan some time. Perhaps because people often pay zakaat during Ramadhaan. 

In the case where there are hundreds of investors in a company or example a property, it's not possible for them to provide each investor their zakaat calculation according to each persons individual date. It would be too much work. What should one do in this situation? 

I have been paying the zakaat on my own Rajab date, and when the investments calculations come through in Ramadhaan, then I discharge that amount as well, with a bit extra.

Zakaat on a gold plated necklace

Q: I would like to query regarding 18k gold plated necklace. 

I previously was not aware that zakaat was due on my 18k gold plated necklace. I'm not sure how long I had it in my possession. I am just going to estimate 13 years. I recently also gave the necklace away within this current year. 

I am not sure how much the necklace weight is: will estimate 18 grams, since I am not sure of the percentage/weight of the "gold" in it. 

Will it be okay if I calculate the zakaat on the current selling price of the necklace e.g. The current selling price is R1200 and then to make up for the 13 years =R 15 500 and then pay 2.5% of this amount, will this be allowed ?

Wife discharging zakaat on her gold for previous years

Q: I have been married around 15 years, and my wife was give more gold ornaments by their parents! There is zakaat to be given for it and she did not provide it! I don't have any gold or savings! Only my wife's gold! How can I calculate the zakaat for the past 15 years => Gold price was low to high till now. Do I need to calculate the yearly gold rate on that year! Can tell me how to discharge the zakaat for the past years?