diff --git a/accounts/config/config-tags.ledger b/accounts/config/config-tags.ledger
index e7ad1b82334ed943c6673a1bf3b434d7d037b746..d222b789009045f12bcdac5433fa1f5e2496debf 100644
--- a/accounts/config/config-tags.ledger
+++ b/accounts/config/config-tags.ledger
@@ -33,3 +33,9 @@ tag Invoice
     assert value =~ /[^\/].+/
     check value =~ /[^\/][^ ]+(\/[^ ])+/
 
+; IncomeType refers to the types of income a non-profit can receive.  In this
+; example, it's for the categorizations on the USA Form 990.  This could be
+; changed to accomodate other jurisdictions around the world.
+
+tag IncomeType
+    assert value =~ /^(Donations|RBI|UBTI)$/