I have some questions with regards to khums please.

1) We have never given khums until now and run a small business. All we have accumulated as savings for the last 10-15 years is what we have now. Should we just calculate 20% on our current saving that we have right now or we have to go back 10-15 years back in time to check our savings each year and give khums on that?
Please clarify.

2) We have a house for investment purpose built on pure savings. It is not sold yet. Do we still have to calculate the amount of current value and give khums on it OR khums is applicable when the house is sold for profit?

1) Yes, you need to calculate your savings from the beginning, and on annual basis, taking into consideration, that you need to pay the khoms of the annual increase in savings.

2) Yes, with the current value.