# Keep leading zeroes and retain corrections

Find a missing-zero mismatch, record a corrected check and retain both observations.

Source: https://help.smartfact.ai/matchbench/guides/zero-correction

Audience: Operator

## Keep leading zeroes and retain corrections

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. **Find the missing leading zeroes**

   Find the missing leading zeroes.

   The value 17 differs from 000017. These are exact strings, not interchangeable numbers.

5. **Record a corrected comparison**

   Record a corrected comparison.

   Submit the complete value again. The corrected check is added, while the earlier mismatch remains available for review.

6. **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=zero-correction&chapter=zero-correction)