NetSuite supports field type conversions for some custom field types. After you have created a custom field, you can edit the type definition to change the Type field to another supported field type. Earlier if you convert one custom field into any other type, the data will be lost. NetSuite now supports field type conversions for some custom field types.
Supported Field Type Conversions
From field type
Decimal Number/Percent/Currency
To field type
Integer Number
From field type
Decimal Number/Percent
To field type
Currency
From Field Type
Checkbox/Currency/Date/Date-Time/Decimal Number/Email address/ Free form text/Help/Hyperlink/Inline HTML/Integer Number/Password/Percent/Phone number/Text area/Time of day
To field type
Free form text/Text area
From Field Type
Select
To Field Type
Multiple select
From Field Type
Text/ Text Area
To Field Type
Rich Text/Long text
From Field Type
Date
To Field Type
Date/Time