Discharging one's zakaat on valuations given of investments

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.