Although, as you correctly state, this Law is not at present applicable to the friends in the West, any believer is free to observe it if he wishes.
This Law of the Aqdas stipulates that nineteen per cent of one's capital is payable as Huqúqu'lláh when such capital has reached an amount of at least "nineteen mithqáls in gold".... In determining the amount a believer should pay, he should first deduct any debts and expenses he may have, and pay nineteen per cent of the remainder of his capital if it is equal to at least nineteen mithqáls of gold.
If you decide that you wish to observe this Law of the Aqdas at the present time, you should determine the total value of your inheritance in cash and other assets less any expenses or debts you may have, and consider the circumstances under which you may be able to pay Huqúqu'lláh on the net value of your inheritance. The time and conditions of payment are left to each individual.
For example, if one's assets include property or shares in addition to cash, he may find it disadvantageous or inconvenient to pay nineteen per cent of the value of the non-cash assets until they are disposed of, at which time he would prefer to fulfil this spiritual obligation. Any expenses that may be involved in disposing of one's assets should be deducted before calculating the net value on which Huqúqu'lláh is payable.
- The Universal House of Justice (From a letter dated 21 January 1973; The Compilation of Compilations, vol. I, Huququ’llah)