These are the responses we received from the offices of the grand maraji’:

The office of the Grand Ayatullah Sistani (may Allah prolong his life): You are allowed to keep your khums with you until you get the chance to pay it to the Grand Ayatullah’s representative.

The office of the Grand Ayatullah Makarem Shirazi (may Allah prolong his life): You can refer to the section of the Grand Ayatullah’s website dedicated to these financial matters and take care of your issues there.

The response of Ayatullah Mahdi Hadavi Tehrani (may Allah prolong his life) in this regard is as follows:

You can transfer the money via internet or bank to the qualified mujtahid or his representative and it is better to submit it to the Islamic supreme leader or his representative. In any case, without specific consent of the mujtahid or his representative, you cannot pay that money to anyone else.

Link to the Istifta’at site