# Fishbowl: Cannot modify custom field with existing data

> You're trying to change a custom field, but existing records contain data in that field.

## What it means
When a custom field contains data in records, Fishbowl prevents you from changing its type to avoid data conflicts. This is a data-integrity guard. The error message suggests creating a new field with your desired type and inactivating the old one.

## What to check
- Confirm you're attempting to change the field's data type (not renaming or other properties)
- Verify which records have data in this field
- Decide whether you need to preserve the old data or accept starting fresh with the new field
- If migrating, plan whether to manually copy data to the new field or leave historical values unchanged

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*From Israel Lopez Consulting (ILC). Custom Fishbowl Inventory integrations and software, and Fishbowl experts since 2015. Written by Israel Lopez. Questions about this topic, or want to reach the people who wrote it? Visit https://israellopezconsulting.com/contact*