You can create custom fields within QuickBooks itself, and these custom fields will sync over to Method, however, some custom fields may have limitations.

Currently, Method syncs with QuickBooks custom fields on the following tables:

While custom QuickBooks fields do sync with Method, its usage on line items in Method is somewhat limited.

When creating a new transaction of the types listed above, or working with one of these transactions that has not yet posted to QuickBooks, you may enter or modify data in the QuickBooks custom fields on your line items. 

If you attempt to modify custom fields on an already-posted transaction in Method, these changes will not be reflected in QuickBooks. Once the sync takes place, the data in Method will be “rolled back” to reflect the data that is still in QuickBooks. Please keep this in mind when performing customization with QuickBooks custom fields.

This is due to a limitation with the QuickBooks SDK. The SDK is what allows Method to communicate and sync with your QuickBooks file. The SDK allows for Method to write data to these custom fields when adding a new record. It also allows Method to read the data from these fields for records that already exist in QuickBooks. It does not however, allow Method to modify data in these fields if the record already exists in QuickBooks.

QuickBooks Desktop has a limit to the number of custom fields you can add within QuickBooks itself. 

(Method allows you to create as many custom fields you want, but these fields will not be synced over to QuickBooks.)

The following is a list of limits based on the version of QuickBooks: