Your Tourist, Business or Private Russian visa must be registered with the Russian authorities if you are planning to stay in Russia for longer than 3 days.
The visa registration in Russia was introduced in a bid to minimise illegal immigration from some CIS countries but as it is a law now, everybody else must follow it. The registration comes as a stamped slip of paper confirming the completion of the registration process. Actually, you do not have to register your Russian visa yourself, your accommodating party – hotel, friends or relatives – should do it on your behalf. Remember to remind them to do it for you. If you fail to register your Russian visa, you may have to pay a fine, be detained by police and even get deported from Russia with the ban of entering that country for up to 5 years. You should get your visa registered within 3 working days and your tickets which you used to enter that country come as proof of your period of stay there.
If you are staying in a hotel, it must register your visa. They will ask you for your passport with the Russian visa and your migration card which is given at the Russian border. Hotels usually charge a small fee for registering visas and it may take from a few minutes to a whole day for them to do it. Some hotels do not have their own registration service but they can arrange it on your behalf for a fee. Hostels usually register your Russian visa only if it was issued through them and they will want you to stay with them for at least one night, otherwise they may refuse to register your visa for Russia.
If you are going to stay with your friends or family in their flat or if you intend to rent, the person who legally occupies the flat will have to get your visa registered. There is no need for you to be present at this procedure, the person who is going to do it for you will only have to bring to a local post office or police station their passport and copies of your passport with the visa and your migration card. The stamped detachable part of the Arrival Notification form will come as the proof of your visa registration. Before you leave Russia or change accommodation, you must remember to hand back this slip to the person who obtained it for you. Thus, the Russian visa registration must be completed every time you enter that country or move from one flat/hotel to another.