Part numbers and item records

Give every part one number, once. Then use that number everywhere. That one habit saves more trouble than any other in a BOM system.

A part number is an identifier for a particular part design. Within one business, and sometimes across several, it picks out one design and no other.¹

Item records first

Most systems keep a record for each part, often called an item. The BOM lines point at those records. In the ERPNext manual, the item is on the list of things you're advised to create before making a BOM.²

When you choose the item for a BOM, the manual says the name, unit of measure and currency are fetched automatically.² That's the payoff. You type the details once, in the item record.

Use your own number, not the supplier's

A supplier's number is theirs. A business using a part will often use a different part number than the manufacturers do.¹

Take a common screw that several makers sell to the same specification. If you use one maker's number, it can look as though only that maker's screw is acceptable. The Wikipedia article says a business also wants a consistent format for the numbers of all its parts.¹

Keep the supplier's number as a separate field on the item. Many systems have somewhere for it. Check your tool's help pages.

Meaningful codes or plain sequence

There are two common styles.¹

• Meaningful ("significant") codes. The letters and digits tell you something about the part, such as its type or size. Wikipedia notes that these help identify an item from its code rather than a long description.¹
• Plain ("non-significant") numbers. They're given out in order or arbitrarily.¹

Wikipedia says non-significant numbers are easier to assign and manage.¹ It also warns that variations can arise when codes are used by other companies, such as your distributors.¹

For a small shop, plain numbers are less work. You don't have to invent a code scheme and then argue about it. A short description on the item record does the explaining.

If you do want some structure, a plain number can still start with a category prefix. Keep it short.

Dash numbers

You'll see part numbers like the same base with a suffix, such as a hyphen and a digit. These suffixes are called dash numbers.¹ Many shops use them to group detail parts or sub-assemblies that belong to one assembly or part family.¹

Whatever suffix rule you pick, write it down. Someone else will need it.

Part number or serial number

These aren't the same. A part number is for the design. A serial number is a unique identifier of one physical unit made to that design.¹

Two identical brackets share a part number. Each could have its own serial number, if you track them. Most small shops don't track serial numbers for every bracket, and don't need to.

Same part twice on one list

Sometimes a list needs the same item on more than one line. One ERPNext manual option, "Allow Same Item Multiple Times", exists for this. Its example is two pipes of equal length that form another shape, where a simple quantity of two doesn't give you the right result.²

Check whether your own tool allows this, and how.

Before you load the list

Clean names are cheaper to fix now than later. Walk through the parts you already use and decide:

• one number for each part
• one name format
• where the supplier's number goes

Then you can build lists from clean records. The step after that is knowing how changes get recorded. The page on recording changes to a list picks up from here.