Validation Expression for a Tax Id Number

I am trying to write the validation expression for a field

that can contain a Tax Id number (format of: 73-1234567)

OR a Social Security Number (format of: 439-66-8888).

I know what the expression would be for each of them

separately but do not know how to combine them so

that each type of format is validated for.

Can you have two validating expressions in one

required field validator? Can you someone help me

with the code?

Thanks,

Stephanie

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