Adding a data item to an Entity

[Len]

I would like to add a check number to the entity EftAccount.  I have added 
the field definition to my entitymodel.xml file (see below).  This has 
correctly added the column to the table definition.
How will the calls to existing services, for example 
'addPyamentMethodToOrder', know to also update this field?

entitymodel.xml
<extend-entity entity-name="EftAccount">

<field name="checkNumber" type="name"></field>

</extend-entity>