I've been on the Washington DC Metro website and see that exact change is required but cannot find any information about whether it must be in coin or if dollar bills are accepted. Can anyone help me out? I need to get fare money from the bank and want to make sure I'm getting the right type.

Thank you.

Yes, they accept coins and small bills. If you will be using the system quite a bit, you may want to spring for a smartcard.

Please be aware that Metro bus drivers do not carry money. You have to have the EXACT FARE if you are paying in cash.

ALSO...if you're taking both metro and bus, be sure to get a bus transfer ticket at the metro station (when you're on your way to board) to help cut down on your bus fare costs. I think a bus transfer still only costs $0.35 for the time period shown on the transfer.

I'll second the Smartrip card. No handling of cash and no hassle with transfer slips.

Don't bother with a Smartcard unless you will be using Metrobus daily for two weeks or more or will be parking in a Metro garage/lot. It costs $5 for the card alone, before you add value for fares and parking fees, and it does not give any discount except a few cents on bus rides. At a savings of no more than 20 cents per bus ride, you'd have to take at least 25 bus trips to recoup the initial cost of the card. The convenience might be worth it to you, but the cards must be purchased on-line, at Metro parking garages, or Metro sales locations, not at subway stations.
Though Metro parking facilities require payment via Smartcard, there's no charge on weekends.
Look at Metro's website for details:

www.wmata.com

I'm a very frugal traveler but it seems a small price to pay -- same as a halfsmoke and coke -- for not having to come up with the correct coins every time you board a bus or remembering to grab and keeping paper transfers (which you don't need with a Smarttrip).

Plus, you can buy the cards at 43 stops along the system (not only in garages, i.e., the Forest Glen and other stations) and Metro Center, which is the system's hub.

This likely won't help the OP but not all parking Metro garages require Smartrip. Anacostia, Franconia-Springfield, Largo Town Center, Vienna/Fairfax, Shady Grove and New Carrollton will take credit cards.

Another benefit of a SmarTrip card is that the paper fare cards are easily desensitized - anything from a credit card in your wallet, to being wet or too crumpled, to the magnetic button of a handbag will render them useless. Then, you have to go to Metro Center, wait in what is usually a long line (assuming it's not an evening/Sunday when they're not open), and trade it in for another functioning one. You can also mail it off for a replacement by getting an envelope from a station agent, but that's probably not so helpful for out of town visitors. Of course, if you're not from here, you may not know you need to go to Metro Center, and the station agents can be less than helpful. It is a pain.

This has happened to so many of my out of town guests that I purchased a few spare SmarTrip cards for guests to load up and use. I personally have been using the same SmarTrip card for several years, and have never had a problem with it. Also, you can register a SmarTrip card online, allowing you to recover the value if it's lost. If you're planning to make more than a few metro or bus trips, I'd consider it worth it.