MOTIONS & REMEDIES — RULE 35

Rule 35 Sentence Reduction

Rule 35 of the Federal Rules of Criminal Procedure holds two very different tools: a narrow 14-day window to fix a clear sentencing error, and a powerful mechanism to reward post-sentencing cooperation. The catch on the powerful one is that only the government can pull the trigger — which shapes everything about how it works.

LAST REVIEWED: July 5, 2026 · FEDERAL SYSTEM ONLY · EDUCATIONAL — NOT LEGAL ADVICE

TIME LEDGER — CASE FILE SUMMARY GOVERNMENT HOLDS THE KEY

Rule 35(a)	Correct a clear error within 14 days of sentencing
Rule 35(b)	Reduce a sentence for post-sentencing substantial assistance
Who can file 35(b)	The government only — not the defendant
Typical 35(b) window	Usually within one year, with exceptions for later-useful information
What it rewards	Substantial assistance in investigating or prosecuting others
Related tools	Other sentence-reduction motions

Two rules under one number

Rule 35 is really two separate mechanisms that happen to share a number, and confusing them causes real problems. Rule 35(a) is a narrow error-correction tool: within 14 days of sentencing, the court may correct a sentence that resulted from arithmetical, technical, or other clear error. Rule 35(b) is a cooperation tool: on the government's motion, the court may reduce a sentence to reward substantial assistance provided after sentencing.

They differ in who can invoke them, when, and why. Understanding which one applies to a given situation is the first step, because the strategy and the realistic odds are entirely different. This page covers both, with most attention on 35(b), which is where the larger opportunity — and the larger frustration — usually lives.

Rule 35(a) — the 14-day clear-error window

Rule 35(a) exists to fix obvious mistakes quickly. If a sentence contains a clear error — a miscalculation, a technical mistake, an obvious oversight — the court can correct it, but only within 14 days of the oral pronouncement of sentence. That window is short and strict, and it is not a vehicle for reargument or second thoughts; it is for genuine, evident error.

Because the window is so tight, Rule 35(a) is usually a matter for counsel to raise immediately at or just after sentencing. For most people researching sentence reductions long after the fact, 35(a) has passed, and the relevant tools are elsewhere — §2255 motions, compassionate release, or 35(b) cooperation.

Rule 35(b) — rewarding cooperation

Rule 35(b) is the mechanism to reward substantial assistance a person provides after sentencing — helping investigate or prosecute someone else. It is the post-sentencing cousin of a §5K1.1 departure, which rewards cooperation before sentencing. When the government moves under 35(b), the court can reduce the sentence, sometimes substantially, to reflect the value of the assistance.

The defining feature is that the motion belongs to the government. A person cannot file their own 35(b) motion; they can only provide assistance valuable enough that the government chooses to file. This creates an inherent imbalance, and it is the source of most of the disappointment around Rule 35(b) — people who cooperated and then waited for a motion that never came.

Why only the government can file

The structure reflects a deliberate choice: the value of cooperation is something prosecutors are positioned to assess, and the decision to reward it is left to them. A person can make clear they are willing to cooperate, can provide genuinely useful information, and can — through counsel — communicate with the government about it. But they cannot compel a motion.

There are narrow limits on prosecutorial discretion here; a refusal to file that is based on an unconstitutional motive, or that breaches a plea agreement's express terms, may in rare circumstances be challengeable. But those are exceptions. As a practical matter, 35(b) relief depends on the government deciding the assistance warrants it, which is why any cooperation should be handled carefully and with counsel.

The realities of cooperation

Because Rule 35(b) depends entirely on the government's decision to file, families should approach cooperation with clear eyes. Cooperation carries real risks — to safety, to relationships inside, and to the person's standing — and it does not come with a guarantee of reward. The value of assistance is assessed by prosecutors, and even genuinely useful cooperation may not produce a motion if the government concludes it did not rise to the level of substantial assistance.

This is why cooperation decisions belong with counsel, not with hallway advice or self-help filings. An experienced attorney can communicate with the government about the assistance, document its value, and press appropriately for a motion where one is warranted, while helping the person weigh the genuine risks. The person's role is to provide truthful, valuable information; the lawyer's role is to advocate for it to be recognized. Neither can force the government's hand, but skilled advocacy meaningfully improves the odds that real assistance is rewarded.

Timing and the value of information

Rule 35(b) motions are generally expected within one year of sentencing, but the rule recognizes exceptions — notably where the useful information did not become useful until later, or where the person could not have anticipated its value. This means cooperation that bears fruit years down the line can still, in the right circumstances, support a late 35(b) motion.

For families, the practical takeaway is that cooperation is a long game controlled by the government, and expectations should be realistic. Documented, counsel-guided communication with the prosecution about the assistance and its value is the appropriate channel — not self-help filings, which do not exist for 35(b).

Where Rule 35 fits among the tools

Rule 35 is one instrument in a larger set of sentence-reduction mechanisms, and it is important not to fixate on it if it does not fit. For clear legal or constitutional errors, a §2255 motion is the vehicle. For extraordinary and compelling circumstances, compassionate release under §3582(c)(1)(A) may apply. For retroactive changes in drug law, First Step Act retroactivity may help.

Our overview of sentence-reduction motions maps how these tools relate, and our guide on when you need a lawyer helps distinguish the situations a person can handle pro se from those that call for counsel. Rule 35(b), because it runs through the government, is firmly in the latter category.

Frequently asked questions

What is a Rule 35 sentence reduction?

Rule 35 of the Federal Rules of Criminal Procedure has two parts: Rule 35(a) lets a court correct a clear sentencing error within 14 days, and Rule 35(b) lets a court reduce a sentence — on the government's motion — to reward substantial assistance provided after sentencing. They're different tools that share a number.

Can a defendant file their own Rule 35(b) motion?

No. A Rule 35(b) motion for substantial assistance can only be filed by the government. A person can provide valuable cooperation and, through counsel, communicate about it, but they cannot compel a motion. This is the source of most frustration with 35(b) — cooperation that never results in a government filing.

How long after sentencing can a Rule 35(b) motion be filed?

Generally within one year, but the rule allows exceptions — notably where information didn't become useful until later, or where its value couldn't have been anticipated. So cooperation that bears fruit years later can, in the right circumstances, still support a late 35(b) motion, at the government's discretion.

What's the difference between Rule 35(b) and a 5K1.1 departure?

Both reward cooperation, but timing differs. A §5K1.1 departure rewards substantial assistance provided before sentencing and is considered at sentencing. Rule 35(b) rewards assistance provided after sentencing, through a later government motion to reduce the sentence already imposed.

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