diff --git a/base-label/outputs.tf b/base-label/outputs.tf
index 2c96211..e40d7fc 100644
--- a/base-label/outputs.tf
+++ b/base-label/outputs.tf
@@ -1,4 +1,4 @@
 output "version" {
   description = "Module version information. Cannot be passed back in tags because it will overwrite other module tags"
-  value = local.base_tags
+  value       = local.base_tags
 }
diff --git a/base-label/prefixes.tf b/base-label/prefixes.tf
index fa3bccb..92f751d 100644
--- a/base-label/prefixes.tf
+++ b/base-label/prefixes.tf
@@ -1,6 +1,6 @@
 locals {
   _prefixes = yamldecode(file(format("%v/prefixes.yml", path.module)))["prefixes"]
-  prefixes  = { for k, v in local._prefixes : k => v!=null ? format("%v-", v) : "" }
+  prefixes  = { for k, v in local._prefixes : k => v != null ? format("%v-", v) : "" }
 }
 
 output "prefixes" {
diff --git a/base-label/variables.tf b/base-label/variables.tf
index cac7451..94bee02 100644
--- a/base-label/variables.tf
+++ b/base-label/variables.tf
@@ -1,19 +1,34 @@
+variable "filename" {
+  description = "Filename of YAML file with tags (see documentation for structure)"
+  type        = string
+  default     = null
+}
+
+variable "filenames" {
+  description = "Filenames of YAML file with tags (see documentation for structure).  Each will be processed and the resultant tags merged"
+  type        = list(string)
+  default     = []
+}
+
 variable "business" {
   description = "Business label (organization, program, etc)"
   type        = string
+  default     = null
 }
 
 variable "application" {
   description = "Application label"
   type        = string
+  default     = null
 }
 
 variable "environment" {
   description = "Environment label"
   type        = string
+  default     = null
 
   validation {
-    condition     = contains(["dev", "test", "qa", "uat", "ite", "stage", "prod", "cre", "sa", "services", "common"], var.environment)
+    condition     = contains(["dev", "test", "qa", "uat", "ite", "stage", "prod", "cre", "sa", "services", "common"], var.environment) || var.environment == null
     error_message = "The var.environment value invalid. See https://github.e.it.census.gov/terraform/cloud-information/tree/master/aws/documentation/naming-tagging-standard for valid list."
   }
 }