It's not over until it's over! Even after you've had an OIC successfully negotiated for you, there are stipulations that could jeopardise all the hard work and money you invested. It is expected the taxpayer will have no further delinquencies. If taxpayers do not abide by all the terms of the agreement (including filing all future returns on time and making all payments when required for 5 years or until the offered amount is paid in full, whichever is longer), their OIC may be declared in default.
The IRS will not give you a second chance or allow you to say "whoops." This is another reason to consider whether an OIC is your best option. There are 20 other resolutions, viable options, that could satisfy your obligation to the IRS. If you can't pay all the required payments as scheduled, you risk defaulting.
Financial hardship is not taken into consideration after an OIC has been accepted. Under-reporting, or not paying current taxes is not an option. A fresh start or freedom from enforced collections can be realized through many other resolutions.