Еще идея про налоги и ИИС

Игнатий, обычно если даже у меня есть мнение о том как устроено в мире, но я давно на эту тему «у них» ничего не читал, то проверяю есть ли опровержение моего мнения. 

Вбейте просто bond traiding accrued interest в поисковиках. 

www.futunn.com/en/learn/detail-what-is-the-accrued-interest-in-bond-trading-73242-221170014
app.achievable.me/study/finra-series-7/learn/bond-fundamentals-trading-accrued-interest

так то что у нас, что в Штатах, в стаканах и на графиках net price, без купона. Но сделка проводится вместе с ним. 

И что касается корректировки налогооблагаемой суммы если был НКД при покупке:
www.investopedia.com/terms/a/accrued-interest-expense.asp

However, since the buyer did not earn all of the interest accrued over this period, they must pay the bond seller the portion of the interest that the seller earned before selling the bond. For example, assume a bond has a fixed coupon that is to be paid semi-annually on June 1 and December 1 every year. If a bondholder sells this bond on October 1, the buyer receives the full coupon payment on the next coupon date, which would be December 1. In this case, the buyer must pay the seller the interest accrued from June 1 to October 1. Generally, the price of a bond includes the accrued interest and this price is called the full or dirty price.

The accrued interest adjustment decreases the taxable interest income by deducting the extra amount of interest that is paid to the new owner of the fixed income security. The accrued interest adjustment is subject to the same laws of taxation as is ordinary interest. The amount of the accrued interest adjustment will always vary, according to the number of days that elapse between the last payment date of record and the date of conversion.