borgata certificates note
 

Borgata in Atlantic City is linked with MGM and Boyd casinos. One can redeem comp dollars at the Borgata (minimum $50) for Borgata certficates (these are valid for 9 months from the date of issue.) [Borgata Comp dollars expire after 6 months.]
If you are a staying as a guest at MGM or Boyd properties, these certificates can be used as CASH to pay anything chargable to your hotel bill (including tips, for example.)
In AC comp dollars do not cover tips, and in the shops comp dollars are on a 2:1 basis.
The only "catch" is that excess comp dollars are not returned. Example, you redeem $100 in certificates and your outstanding charges are $96--you lose $4.) Also, many casino front desk employees have never seen these and always need assistance in how to handle them!
[Funny note: I was staying at Bellagio and charged meals and tips to my room, my room was comped, and after subtracting off my certificates, I owed 4 cents--which they insisted on my paying, and I did in pennies.:)]