There are several similarities between Islam and Christianity as both have the same belief in One God. In Islam religion, it’s a mandatory belief that all the four holy books were sent by the same God, Allah. Namely Quran, Torah, Injeel (Bible) and Zaboor, but all these were sent on different prophets. Hence the message they carry is the same whether it is read from Quran or Bible. However, there are minor differences as few rules were changed in the most recently sent book Quran. The current bible has a lot of changes that have been made by men and changed several commands of God. So it’s not in its pure form as it was originally revealed. But Quran is in its pure form as Allah promised that He wouldn’t let change is the final book.
Similarities are that Islam prohibits interest in any loans, whether business related or any other. In conducting business, it is mandatory to keep our buying and selling honest. And when one party lends some money to the other, there must not be any interest involved. Whether any bank is involved between or any other institution, it must be free from Riba (interest). Islam addresses that all buying and selling must be with fair dealing and at fair prices.
If one person takes a loan, then he will return the same amount to the lender. No per cent amount can be added to it. It is extremely prohibited and not allowed. If anyone takes interest, then his earnings are not legal.
In Christianity, basically, interest is not allowed, but new laws have changed it a bit, making it the way that only with relatives and your brother you cannot take interest while with all others who are strangers, interest may be allowed. Christianity also preaches fair dealings and honest commencement of business among parties.