The local currency is the Trinidad and Tobago dollar (TT$), divided into one hundred cents. Coins start at 1 cent and range up through 5, 10 and 25 cents. Notes start at 1 dollar (so 10 pence can feel like a lot in your wallet!) and are in denominations of 5, 10, 20 and 100.
Keep some in small denominations as supermarkets and bars may exchange $100 but taxis and street vendors often can't and should be paid with $20 or less. Although the exchange rate varies, the easiest way to work out how much you're spending is $10 to the £1, so $100 would be approximately £10.
Most restaurants, high-class shops and hotels accept Travellers' cheques and credit cards and you will need to show your passport or driving license for identification, but in smaller establishments and rural areas they are unlikely to take anything but local currency although some places will also accept US dollars. There are banks to change money in Crown Point and Scarborough, and plenty of cash machines (ATM) that accept most credit cards around the Island however you are usually charged for the withdrawal.