A tax shelter product designed to create large, seemingly real losses to be used for tax sheltering. This tax shelter involves creating a shell company, which enters into a long chain of sophisticated and complex financial investments. These investments usually create fake accounting losses that are more than 100 times larger than the real financial loss. Ultimately, these large losses are then used to offset legitimate capital gains, allowing the tax shelter's creators to pay less tax.

OPIS represents only one of the many unethical tax shelter products that were used in the late 1990s. As these abusive strategies became more and more popular, the IRS started to perform audits on those using this strategy in order to dissuade its use.

By the time the IRS took action, millions, if not billions, of tax dollars were being defrauded. For example, one OPIS user spent about $550,000 to create a fake accounting loss of $60 million. Although the use of OPIS was eventually stopped, other unethical tax sheltering strategies, such as bond linked issue premium structures (BLIPS), emerged to take its place.