You can use RowNumber function to do that. Add a new Empty Column to your tablix and then click on Cell and go to Expressions and write expressions as shown below.
=RowNumber("DataSet1")
Notice that I have used "DataSet1", that is the scope. That means we would like to generate sequence number or row number for all the records in our Dataset.
If you want to start a new row number sequence for your each group, you can provide Group Name in your scope.
=RowNumber("DataSet1")
Notice that I have used "DataSet1", that is the scope. That means we would like to generate sequence number or row number for all the records in our Dataset.
If you want to start a new row number sequence for your each group, you can provide Group Name in your scope.
How to use RowNumber Function in SSRS Report - SSRS Interview Questions and Answers
You can see the sequence number is generated for our all the records in our SSRS Report.