Hi 

Whilst not a priority it would be very useful to be able to set validation on the custom customer fields as created in Settings, Customer fields.

For example  field type  create as   Date - this would  only permit valid dates  to be entered , optionally permit   future, past or any date.

 Field Type   create as Numeric -  input  must be numeric  optionally set to 2 DP

A more complex but really wonderful option would be to allow the creation of drop boxes,  Take a look at how Zendesk or Freshdesk do this.  Basically both software systems allow drag and drop creation of drop boxes and dependant lists.

 The introduction of validation will make the  data held in custom fields much more reliable, and eliminate typo's if the field is being used to categorise  or date something

Now if we could get that  those custom fields  into invoices and email templates as substitution well........

That  would be really brilliant.