diff --git a/app/models/validations/sales/financial_validations.rb b/app/models/validations/sales/financial_validations.rb
index 72b80874b..18ae9974f 100644
--- a/app/models/validations/sales/financial_validations.rb
+++ b/app/models/validations/sales/financial_validations.rb
@@ -122,7 +122,7 @@ module Validations::Sales::FinancialValidations
     elsif record.numstair
       # We must use the lowest possible percentage for a staircasing transaction of any saletype, any year since 1980
       minimum_percentage_per_staircasing_transaction = 1
-      previous_staircasing_transactions = record.numstair - 1
+      previous_staircasing_transactions = record.numstair - 2
 
       if percentage_left < previous_staircasing_transactions * minimum_percentage_per_staircasing_transaction
         equity_sum = sprintf("%g", record.stairowned - percentage_left + previous_staircasing_transactions * minimum_percentage_per_staircasing_transaction)