Settlement by agreement: means to fund the offer: degree of difficulty
In many SI cases there is a means problem of some kind.
Whilst the problem is widespread, the degree of difficulty varies enormously. At one end of the scale is the taxpayer that has sufficient means to comfortably fund full settlement but needs time to convert fixed assets to liquid funds.
At the other extreme are taxpayers that are bankrupt with no net assets and with scant prospect of achieving future income through age or disability.