The following article is an overview of what regulation CFR (Code of Federal Regulations) Section 42 Subpart C is at a point in time and how it can be applied with the Quality Inspector app; the regulations may have changed after this article was written.

You can find regulation details on the following United States Government links:

• Subpart C—Skip Lot Sampling and Inspection Procedures
• CFR-2010-title7-vol2-sec42-121
• CFR-2025-title7-vol2-sec42-122
• CFR-2025-title7-vol2-sec42-123

CFR (Code of Federal Regulations) Section 42 Subpart C outlines the U.S. Department of Agriculture’s official sampling and inspection procedures for agricultural products, including the rules for moving between normal, reduced, and skip-lot inspection levels based on lot acceptance performance. In the context of skip-lot, it defines when you are allowed to inspect only selected lots instead of every lot, and when you must revert back to inspecting every lot if a failure occurs.

You can use Quality Inspector’s skip-lot feature to help implement skip lot procedures as specified in CFR Section 42 in Subpart C Skip Lot Sampling and Inspection Procedures from sections 42.120 through 42.123.

CFR Section 42: Skip-Lot Sampling and Inspection

CFR Section 42 Skip-Lot Sampling and Inspection is a controlled method for evaluating stationary lots in which 25% or 50% of offered lots undergo full inspection. By definition this approach is permitted only when the following conditions are met:

• The USDA Food Safety and Inspection Service Administrator has granted authorization, and the method is acceptable to both the inspecting agency user and the producer (if different parties).
• The inspection qualifies as an origin inspection (an inspection made at any location where the filled containers are examined prior to shipment or transfer to the purchaser).
• All lots are expected to have essentially uniform quality. As a process, a skip-lot inspection only works when there is a stable, well-controlled process; if quality varies significantly between lots, skipping lots introduces unacceptable risk.
• The producer’s lots are currently under, or eligible for, normal or reduced inspection.

Example scenarios that might quality for Section 42:

• Automated filling and sealing line running continuously with SPC control and good audit history (you can build audit history over time by creating and recording Quality Inspection Tests).
• Same supplier inputs, same operators, no process deviations.

Example scenarios that likely would not meet the requirement:

• Frequent raw-material changes or variability.
• Multiple uncontrolled production lines feeding lots into the same pool.
• Known process issues or recent non-conforming lots.
• Seasonal or unstable production cycles.

If your customer wants to do reduced testing or reduced sampling, but they do not quality for skip-lot procedures, you can demonstrate other sampling features (such as AQL) tables that can help.

Section 42: Skip-Lot Sampling Procedures

• After 10 consecutive acceptable lots, begin skip-lot by inspecting one-half of the lots under normal inspection procedures.
• After 10 consecutive acceptable inspected lots while at the one-half rate, move to inspecting one-fourth of the lots.
• If any inspected lot fails while at the one-half or the one-fourth rate, immediately return to inspecting every lot under normal inspection and restart the sequence.
• The one-half rate may start immediately if the producer is already on, or eligible for, reduced inspection and all other criteria are met.
• Once skip-lot inspection begins, reduced inspection cannot be used—only normal inspection procedures apply.
• If operating at 100% inspection (not at one-half or one-fourth) and the criteria for switching to tightened inspection are met, skip-lot stops and Subpart B procedures take over.
• Skip-lot cannot resume until all eligibility conditions are satisfied again, meaning 10 consecutive acceptable lots must be achieved under normal inspection.

Considerations for consultants when implementing this procedure

• The specification requires percentages; however, customers often give specific numbers as their processes may have typical lot sizes for their facility. If the lot sizes are always consistent, this can sometimes help floor staff by using fixed sizes (for example if lots are always in a quantity of 1260, it may be simpler for the customer to put in 630 instead of defining 50%).
• Randomization in the tightened blocks 3, where it is at the reduced 25%, is best done as a physical activity.
• Consider using sampling (with or without AQL) and which approach makes the most sense for the customer.
  • Sampling: can impact the approach for % and the approach for random sampling, for each you can inspect 100% of each lot offered, and then use sample size to inspect 50%.
  • Percentages: you can use to test a percentage of units within the lot.
• Speed of processing quality inspections. The specification requires 10 passed tests, and you use the Pass Threshold when taken literally; however, you can use Create Threshold (the default threshold process for creation) when inspections are quick. The difference in using either may depend on typical confidence of the pass results in combination with typical speed of the tests themselves. Use Pass Threshold for strict adherence.
• The pass counter and threshold counters are intuitively consecutive counters as it takes one failure to revert back to the first test step.
• Ask the customer how they want to treat block 3. By definition block 3 (25% of the lot) can continue indefinitely as long as all criteria defined in section 42.120 is in place and no failure occurs. This is often the minimum criteria and there are finite limits for the customer before they go back to full or half testing instead of a failure scenario triggering full testing. This walkthrough presumes the typical scenario of some finite limit, and the example used in this walkthrough is arbitrary. Adjust according to your customer’s scenario.

Examples

You can use the following examples as inspiration for your approach, where the best approach depends on the real-world characteristics of the material that is being inspected.

Example 1

Using the procedure to control the sampling percent sizes (e.g., a test is always made, but the skip-lot configuration determines if it is at 100% sampling, 50% sampling, or 25% sampling).

This approach works with receiving large lots, where a test represents a batch of a large known quantity and samples are measured individually with the sampling worksheet, or where the sample quantity is used to represent the quantity being tested (instead of the source quantity).

For food, this helps with the practicality of applying randomization when selecting individual samples by leaving the randomization up to a floor decision.

This interpretation on the percentages is reducing the quantity inspected by percentage, but still inspects each lot.

The reason why you see this interpretation of changing the sample size instead of entire lots is it reduces testing time and helps give a better idea of total quality across all containers.

Example 2

Using the procedure with a known lot size. This would make more sense if the lots tend to be received in consistent lot sizes, or the discrete quantity is small and the lot is tested as a whole. In this scenario, skip-lot would be implemented in the more standard approach with those known lot sizes being adjusted for 50% and 25%.

You would see this interpretation of skipping entire lots when the container or vats are less likely to introduce quality issues.

Example approach 1

Using skip-lot to define changing sampling percentages. The following configuration steps presume that you are combining sampling, and using this procedure to control the sampling percentage of goods.

In this approach, each lot being received is considered, but we will use the sampling percentages to impact how many samples in each lot are tested. Each line is set to Test and instead the percentages are used to determine the sampling amount for each test. The sample quantities themselves end up being used for the 100%, 50%, and 25% sampling rates.

This approach is useful for randomization selection as it is the batch samples that are randomized on the floor.

In the standard flowchart, there are blocks 4 and 5, which are both failure blocks of “Revert immediately to inspection of every lot, go to block 1”; you can set the “Fail Threshold” and “Fail Step No” with Quality Inspector.

Considerations

A special note about “Block 3” in this example.

This example also sets an arbitrary “100” as both the creation and pass thresholds on the 25% testing step of block 3 to go back to 50% testing at block 2, this is not part of the minimum specification but an example of realistic limits that may be set. Since the specification allows 25% sampling in block 3 indefinitely, it is often in the responsible company’s best interest for the material to do more frequent checks.

Companies responsible for materials often implement more stringent quality controls than the minimum skip-lot rules require because regulatory compliance alone does not fully protect business risk, brand reputation, or product safety.

While the regulated skip-lot logic allows remaining at a 25% inspection rate indefinitely if no failures occur, many organizations choose to exceed those requirements because:

• Consumer protection and product safety (food contamination impacting reclass, illness, regulatory penalties, patient harm, or life critical failures).
• Brand reputation, customer trust, and customer perception.
• Contractual requirements or other supply-chain requirements, or Tier-1 supplier contracts that have zero-defect programs.
• Internal continuous improvement protocols.
• Managing risk over time as the consequence of testing equipment wear, vessel wear, staff turnover, changes in raw material, and natural process drift.
• Liability and Insurance requirements

Steps for using percentage changes with fixed percentages in a skip-lot rule

1. Have a quality inspection template for this process, and configure the “Sample Source” to be “Percent of Quantity” with “Sample %” set to “100”.
   1. What this does: by default this will set the ‘Sample Quantity’ on the test to be the full quantity that’s within the lot that’s being received.
2. Create a skip lot rule, and make sure that there is a connection to the template via the Quality Inspection Test Generation rules.
3. In the skip lot rule create a new line.
   1. Set “Count By” to “Occurrence”
   2. Set “Group By” to “Item”
4. In the “Lines” section, if the “Pass Threshold”, “Sample %”, and “Sample Source” columns are not shown then personalize or customize the page and add the “Pass Threshold” field, “Sample Source” field, and “Sample %” field.
5. In the “Lines” section, create a new line for block 1.
   1. in “Step No.” set the “Step No.” to “10”.
   2. Leave Create Threshold blank (see considerations for consultants)
   3. Leave Fail threshold to 1.
   4. Set “Action Type” to “Test”
   5. Set Description to be “Block 1, every lot offered”
   6. Set “Pass Threshold” to 10.
      1. This tells the system that 10 consecutive tests must pass.
   7. Set “Sample Source” to be “Percent of Quantity”.
   8. Set “Sample %” to be 100.
   9. Set “Fail Step No.” to be 10.
6. Create another line for block 2
   1. in “Step No.” set the “Step No.” to “20”.
   2. Leave Create Threshold blank (see considerations for consultants)
   3. Leave Fail threshold to 1.
   4. Set “Action Type” to “Test” (note that it will default to ‘skip’).
   5. Set Description to be “Block 2, one half”
   6. Set “Pass Threshold” to 10.
      1. This tells the system that 10 consecutive tests must pass.
   7. Set “Sample Source” to be “Percent of Quantity”.
   8. Set “Sample %” to be 50.
   9. Set “Fail Step No.” to be “10” (block 1).
      1. In the standard flowchart published by the United States government block 2 goes to “Block 4”, which is just a block indicating that a failure occurred, there is no actual state, it then proceeds directly to “Block 1”.  The fail threshold of 1 and the fail step reference back to block 1 accomplish this.
   10. On the previous Block 1 line, set “Success Step No.” to be the newly created “20” if this isn’t done automatically.
7. Create another line for block 3.
   1. in “Step No.” set the “Step No.” to “30”.
   2. Leave Create Threshold blank (see considerations for consultants)
   3. Leave Fail threshold to 1.
   4. Set “Action Type” to “Test”
   5. Set Description to be “Block 3, one quarter”
   6. Set “Pass Threshold” to 100.
      1. See the integration notes for details. This number is arbitrary for this example, but your customer will likely have some limit above and beyond the minimum requirement defined in sections 42.120.
      2. 42.120 Does not technically require a maximum pass count, however in practice there will likely be a definitely pass count.
   7. Set “Create Threshold” to 100.
      1. See the integration notes for details. This number is arbitrary for this example, but your customer will likely have some limit above and beyond the minimum requirement defined in sections 42.120.
      2. 42.120 Does not technically any minimum create count, however in practice there will likely be a creation count maximum or failure count maximum.
   8. Set “Sample Source” to be “Percent of Quantity”.
   9. Set “Sample %” to be 25.
   10. Set “Fail Step No.” to be “10” (block 1).
       1. In the standard flowchart published by the United States Department of Agriculture block 3 goes to “Block 5”, which is just a block indicating that a failure occurred, there is no actual state, it then proceeds directly to “Block 1”.  The fail threshold of 1 and the fail step reference back to block 1 accomplish this.
   11. On the previous Block 2 line, set “Success Step No.” to be the newly created “30” if this isn’t done automatically.
8. Make sure the appropriate test generation rule is configured to use your new step lot configuration rule.

Blocks 4 and Block 5 in the specification are both failure blocks and don’t need a defined state, in both scenarios they cause full inspection again.