Where do I subtract accreted prepaid interest on my tax exempt muni bond?

I bought a 20,000 municipal tax exempt  bond and that pays 500 dollars interest JUly 1 .  I bought it in /april and paid 20,000 + 300 (prepaid accreted interest) .  IN July I rlecived 500 interest BUT only 200 is the earned interest,  Where do write off /adjust the accreted prepaid interest???