# Change references without rewriting history

Create a second group and compare against its reference.

Source: https://help.smartfact.ai/matchbench/guides/changing-reference

Audience: Operator

## Change references without rewriting history

1. **Start a comparison**

   Start a comparison.

   Use a known reference and check each label separately. These practice values are synthetic. An exact match is not a physical contents or optical approval.

2. **Keep every leading zero**

   Keep every leading zero.

   Enter the complete reference. MatchBench preserves each character exactly, including spaces and leading zeroes.

3. **Move on to checking labels**

   Move on to checking labels.

   The reference stays fixed until you deliberately change it. Each submitted comparison stays in history.

4. **Check an identical value**

   Check an identical value.

   All six characters agree. A match proves only that the decoded values are equal, not that two separate physical labels were scanned.

5. **Choose to change the reference**

   Choose to change the reference.

   Changing the reference starts a new group. Earlier comparisons keep their original reference and outcome.

6. **Enter the new reference**

   Enter the new reference.

   Use REF-002 for the next checks. The original 000017 group remains unchanged.

7. **Move on to checking labels**

   Move on to checking labels.

   The reference stays fixed until you deliberately change it. Each submitted comparison stays in history.

8. **Check the old value against the new reference**

   Check the old value against the new reference.

   The old value now differs because REF-002 is the active reference. MatchBench does not rewrite the earlier exact match.

9. **Check the new reference exactly**

   Check the new reference exactly.

   This value matches REF-002. Both groups and every check remain in the review.

10. **Review every retained check**

   Review every retained check.

   Review the newest check first, with its original reference and recorded entry source. A correction does not delete the earlier observation.

[Watch or practise this chapter](https://help.smartfact.ai/matchbench/demo?guide=changing-reference&chapter=changing-reference)