Vote buying is considered both an illegal practice as well as unethical
in all countries, though it varies how different legal frameworks deal with

Vote buying includes providing a financial or material incentive to a voter
in exchange for a vote, buying abstentions (negative vote buying) or paying
voters to stay home. Borderline cases include the promise of jobs, loans,
promotions etc. to get votes. In Mexico, parties have paid for the organization
and transportation of voters to the polls; something that has been considered a
severe abuse of campaign funds and is considered illegal. In the U.S., 30 states
treat vote buying as an offence of bribery.

The main device used to restrict vote buying is the secret ballot. If votes
are cast in secrecy, there is no guaranteed way for candidates and party
organizers to be certain that the vote was cast according to the agreement
between voter and briber. Despite this, in some communities, the secret ballot
has not proved sufficient to eliminate vote buying altogether.

Vote buying is still common in some countries. Below is an extract from the
ACE website on vote buying in the Philippines, written by Ding Tanjuactco:

Vote buying with or with out chained balloting

Some candidates will take the word of the bought voter. However, if he wants
to be sure that he gets his money's worth, the candidate will employ chained
balloting or "lansadera". At the start of the day, all the potential "buyees"
are gathered in one place and, as soon as the polls are opened, one of them is
sent to the polling place. After the usual identification process, he obtains a
ballot from the poll clerk, which he takes with him to the polling booth.

At this point, everything is still fine and dandy. But what he does with the
ballot becomes the heart of the illegal scheme. Instead of filling up the
ballot, he puts it in his pocket and casts something that looks like a ballot
into the ballot box. Thereafter, he presents the blank official ballot to the
buyer who pays him an amount for his effort. The buyer then fills up the ballot
himself and hands the same to the second voter. The second voter goes to the
polling place and obtains a blank official ballot but does not drop this in the
ballot box. Instead, he drops the ballot which was filled up by the buyer. He
then turns over the blank official ballot to the buyer and the cycle is

(Some voters may bring an eraser to erase the pre-marked ballots and mark it with their own marking for their preferred candidate while in the ballot marking counter.)
Vote buying with or without identifying marks

Another way of ensuring that the bought voter will live up to his end of the
bargain is to specify how that voter will fill up his ballot. The voter can be
required to write the candidate's name in a peculiar way, e.g. first name last,
with nickname, slightly misspelled etc.

Negative vote buying

This is the simplest way of buying votes. Where a candidate is certain that a
voter will not vote for him, he can pay him not to vote. Efficiency can be
achieved by herding the voters together and getting them on a bus that will take
them away for the rest of the day. A lot of times, the voters will be compelled
to have their index fingers smeared with indelible ink.