Tax on Freelance web designer

[Koolestboy]

Hi,
I am little confused about my earning as a freelance Web designer.
Either i have to pay tax or not

i work as a freelance web designer and have clients in US and i get remittance from them in bank through wire transfer.

am i qualified for tax?
its been 6 month to me working in this criteria
earning are not so high but i am worried.
Do i have to pay on every transaction or yearly
what is the limit etc

Please if someone can guide me on this