This only applies if you BOUGHT in secondary, and you pre-paid interest to the seller for what had accrued prior to your purchase. Unfortunately, when this is paid to you later on the next coupon date, your broker will report ALL of that interest to the IRS as yours, so you need to deduct what was prepaid so you don't pay taxes on something you didn't actually earn. Other complication is if your first interest payment occurs in the next tax year (you can only fix this in the tax year in which it is taxed).
Basically, this is a one time problem with the purchase transaction.