The answer depends on one critical document: the Judgment and Commitment Order signed by the sentencing judge.
If that order includes a parole provision, your person could be looking at a parole hearing in about 32 months. Missouri's parole board evaluates cases based on conduct while incarcerated, completion of recommended programming, and the nature of the original offense. A nonviolent first-time offender with a clean institutional record presents a strong case for release at the earliest eligible point.
If the judge did not include parole in the commitment order, the calculation shifts to straight time with good behavior credit. Missouri state prison applies a standard good time reduction, and at 85% of an 8-year sentence that works out to roughly 82 months served, just under seven years.
The difference between those two outcomes is significant, and it all hinges on what the judge put in writing at sentencing. An attorney can pull that document and give you a definitive answer on which path applies.
Either way, the most important thing your person can do starting day one is keep a clean disciplinary record and engage fully with whatever programming is available or recommended. For a nonviolent first-time offender, that track record carries real weight with a parole board and is the single most controllable factor in determining how much of that 8 years actually gets served.
Identity theft and trafficking in stolen identities is treated seriously but is still a nonviolent offense, which generally works in their favor at the parole stage.