Keeping expenses separate is really important for the self employed. This will make doing your taxes so much easier come April.
Depending on your particular industry this could mean you can claim books, magazines, journals, writing supplies, etc... (for writers) or you could be taking concert tickets, iTunes, blank CD's, sheet music and musical instruments (for musicians) off your taxes.
Consult someone who is well versed in taxes for artists as to how much and what can be used for taxes and what can't. Here in Toronto I went to see Amanda Mills of Artbooks to figure out how to configure my business. I learned that I had not been taking enough off my taxes and that I could be claiming thousands more! It's worth it to talk to someone who knows what they're doing.
p.s. Keep your receipts for everything!
