The quick answer
Go to Customization > Lists, Records, & Fields > Item Fields and click New. Give the field a Label and an ID (NetSuite adds the custitem prefix), pick a Type, and on the Applies To subtab check only the item types that need it. On the Display subtab, choose the Subtab where it should appear and add Help text, then save. The field is available on those item types only, and the item form and role still decide who sees it.
The screenshots show sample data. Person and company names are fictional. Use your own field names, lists, and items when following the steps.
Before you start
This example adds a Finish Color field to Birchline Home Goods' items. The choices come from a custom list called Color that already holds Charcoal, Sage, and Sandstone. If you want a List/Record field, create its list first under Customization > Lists, Records, & Fields > Lists.
You need a role that can create custom fields; Administrator is used here. The item types you can choose in Applies To depend on the features your account has turned on. Assembly/Bill of Materials, for example, only shows up when assemblies are enabled.
Decide the field type before anyone starts entering values. Changing it later can invalidate or lose data already on items.
01. Check the item and existing fields
Open the inventory item Enamel Camp Mug. Its Classification group has Department Housewares, Class Drinkware, Shop Floor Category, AM Product Family, and Planner. There's no color field.
Go to Customization > Lists, Records, & Fields > Item Fields. The list has Care Instructions, Carton Quantity, and Gift Wrap Eligible. Nothing is labeled Finish Color. Check this list before you pick a label, because a near-duplicate confuses users, and NetSuite can refuse a label another custom item field already uses.
02. Name and describe the field
Click New. On the Custom Item Field form, enter Finish Color in Label. That's what users see on the item.
Enter _finish_color in ID. NetSuite adds the custitem prefix when you save, so the field ends up as custitem_finish_color. Leave ID blank and you get a generated number instead, which is a pain to reference in searches, imports, and scripts.
Enter Finish color of the item as sold. in Description. Description documents the field on its definition; users don't see it on the item.
03. Choose the field type
Set Type to List/Record. The List/Record field becomes available; set it to Color. Every item now picks from the same three values instead of typing its own spelling of "sage".
Leave Store Value checked so each item keeps its own value. Leave Show In List cleared. Show In List only adds the field as a column in item lists; it doesn't control whether the field is on the item form.
04. Choose the item types
On the Applies To subtab, check Inventory Item and Kit/Package. Leave Service and the other item types cleared. Leave Subtype at Both, and leave Select Individual Items cleared. Checking it would limit the field to specific items you pick, and here you want it on every inventory item and kit.
05. Place the field and save
On the Display subtab, set Subtab to Main so the field goes in the item's main area instead of on a subtab. Leave Display Type at Normal, which lets users edit it. Enter Finish color of the item as sold. in Help. This is the text users see when they click the field's label.
Click Save. The Custom Item Fields list shows Finish Color with ID custitem_finish_color, Type List/Record, List Color, Tab Main, and a Y under Inventory Part.
Scroll the list to the right and the same row has a Y under Kit/Package. The form calls it Inventory Item and the list column calls it Inventory Part; they're the same item type.
06. Set it on an inventory item
Open Enamel Camp Mug and click Edit. On this item form, Finish Color now sits in the Classification group, after AM Product Family.
Click the Finish Color label. Field Help shows "Finish color of the item as sold." Close it.
Open Finish Color. It lists Charcoal, Sage, and Sandstone, the values of the Color list.
Choose Sage and click Save. The saved item shows Finish Color Sage.
Check the result
- The Custom Item Fields list shows custitem_finish_color with Type List/Record, List Color, and Tab Main.
- The field has a Y under Inventory Part and Kit/Package and nothing under Service.
- Enamel Camp Mug shows Finish Color Sage in its Classification group.
- Clicking the Finish Color label opens the help text.
07. Confirm service items stay clean
Open the service item Mug Engraving. Its main area has no Finish Color field, because Service wasn't checked in Applies To.
Where the field lands inside the main area depends on the item form. Here it joined the Classification group after the last standard field. Custom item forms can hide or move it, so check the form each role actually uses, and use Apply to Forms on the field or customize the form if it's missing. If you leave Subtab blank, the field usually lands on a Custom subtab of the item. And test with the role your buyers or merchandisers actually use, not only Administrator.
Common questions
Should a color field be Free-Form Text, List/Record, or Multiple Select?
Use List/Record when every item should pick one value from a controlled list, like Charcoal, Sage, or Sandstone. Free-Form Text lets people type anything, so you end up with "Sage", "sage", and "sage green". Use Multiple Select only if one item can really have more than one color, since it changes how searches, imports, and scripts read the value.
What does the custitem prefix on a field ID mean?
It marks a custom item field. You type the rest of the ID, like _finish_color, and NetSuite saves it as custitem_finish_color. That full ID is what saved searches, CSV imports, and scripts use, so pick a readable one instead of leaving it blank.
What's the difference between Description and Help?
Description lives on the field definition and tells admins what the field is for. Help, on the Display subtab, is what users see when they click the field's label on an item.
What do Store Value and Show In List do?
Store Value saves the chosen value on each item, which is what you want for something people maintain by hand. Show In List adds the field as a column in item lists. It has nothing to do with whether the field shows on the item form.
Why does NetSuite say "This custom field already exists"?
Another custom item field already uses that label or ID. Check the Item Fields list, including inactive fields with Show Inactives, and either reuse the existing field or pick a different label and ID.
Why doesn't my custom item field show on an item?
First check Applies To. If the item's type isn't checked, as with Service in this example, the field isn't available on it. If the type is checked, the item form is the next suspect: custom forms can hide or move the field, so open the form that role uses or use Apply to Forms on the field.