If you are obtaining a visa on arrival, a single trip Kenya visa costs $50  £30 or €40, at Mombasa they always accept all these currencies, they usually accept all these currencies at Nairobi but very occasionally they insist on Dollars at Nairobi. 

If you are from the UK and travelling with Thomson / First Choice you will also need $40 for the departure tax although this can be paid in Kenyan Shillings. If you want to buy duty free at the airport on the way back USD are the best currency (prices are marked in dollars and the exchange rates they use are very unfavourable).

Unless you have arranged to pay for your safari in USD the above are the only USD you will need. Some larger hotels, shops and restaurants may accept them but at a poor rate of exchange. Anywhere that will accept Dollars will also accept Pounds and Euros, but again at a poor exchange rate.

For day to day expenses you will need Kenyan Shillings (KES, /- or 'Bob')  

If you want to take cash, take your local currency ( Sterling / Euros / Dollars) and change into Shillings at either the bank or forex at the airport (while you collect your bags at Mombasa) or at a bank or forex / FX. You will get a better exchange rate in Kenya and you will get the best rates at a forex. You hould avoid changing money in your hotel or Safari lodge as their rates will be poor. You can keep your cash safe in the hotel's safes. 

The best exchange rates on the North Coast are at the Shaban Minimarket and the Unik / Cheers office, both next to Cheers bar at Bamburi beach 

If you want to use credit / debit cards, you can also ATMs at the airport and near the tourist hotels.

If you take your credit/debit card to use in either an ATM or shop etc, let your card company know you will be using in Kenya to avoid embarrassment at the till. This is not the case with ALL credit/debit cards as some allow transactions without pre-informing them. A word of caution - althougth credit card payment is widely acceptable at most major establishments, some charge a levy for non cash-transactions and others like Nakumatt may randomly insist on a ID so best carry your UK drivers licence or Passport to avoid embrassment.

There is a Barclays ATM on the right after you come out of the baggage reclaim area. There is another ATM on your left which you probably won't see because it will behind the line of people trying to get you to use their taxis - this one looks a bit dubious because its in a fairly tatty kiosk but its OK

The exchange rate at the airport isn't brilliant - but is probably still better than your hotel. The exchange rate at the ATM will be better but you will get hit with a charge for using the ATM, and 2.5% to 3% Exchange charge. This is still better than any deal you will get in the Uk, and is usually slightly better than the deal you will get at a Kenyan bank. It is also mthe most convenioent as you don't have to carry acsh, and the ATMs are available 24/7.

Both the bank / forex and the ATM are likely to give you 1000 and 500 shilling notes. If you don't want a lot of money and you just want want smaller denominations for tipping the bank / bureau is probably your better bet. Though you could always get a bottle of water at the Karibu Cafe on your right as you leave the airport building - which would give you some change to get started..

Some people on All Inclusive don’t change money at all and tip in Pound and Euro coins. This isn’t ideal for the locals as FX only deal in notes. If you are approached by a local who asks you to change european coins for shillings or for sterling or euro notes, it is not a scam. They have no other way of cashing in their tips. It is best to tip in Shillings anyway.

 A tip for those who are going on an All Inclusive package or straight to the resort, it may be worth buying some Kenya Shilling in the UK prior to your travel. Reason for this is the resorts in Mombasa can be far away from the malls and areas where you can break your Sterling Pounds and so depending on how far your resort is it may be worth to carry some Kenya Shilling in you. Some high street exchange places in the UK give a decent rate though not as good as you would get in Kenya but for relatively small amounts of cash it will be worth it for the convenience, as it will allow you to buy water, newspapers, give tips straight after you land and not worry about parting precious pounds.

Banks and ATMs

Apart from the airport there are ATMs at the following places

Bamburi beach - 2 ATMs at Barclays 

Nyali - there are half a dozen ATMs in City Mall (aka Nakumatt complex) and one at the Kenoil filling station

Mtwapa -  a Barclays ATM, an ATM at the Kenya Commercial Bank, one at the Kenoil filling station and at the Co-op Bank on the northern edge of Mtwapa

Visa is accepted at all the ATMs listed. Mastercard is accepted at some of the ATMs in the Nakumatt complex  at Nyali and at the Barclays ATMs. Nakumatt also accept it for purchases (ID may be requested at times)

Mombasa

If you want to change money while in Mombasa (on the island), Coast Forex on the roundabout at the bottom of Moi Avenue is airconditioned with individual booths and they may be willing to offer a shilling or two more than the banks. Severeal more Forex exchange places have now opened. One can be found opposite the main market, another two from walking distance from the Central Police Station in old town.