In a Reporting Services paginated report, you can merge cells in a data region to combine cells, improve data region appearance, or provide spanning labels for column groups and row groups.
You can only merge cells within each area of a data region: corner, column headers, group definition (or row headers), and body. You can't merge cells that cross area boundaries. For example, you can't merge a cell in the data region corner area with a cell in the row group area. Read more about Tables, Matrices, and Lists (Report Builder and SSRS).
You can create and modify paginated report definition (.rdl) files in Report Builder and in Report Designer in SQL Server Data Tools. Each authoring environment provides different ways to create, open, and save reports and related items.
To merge cells in a data region
In the data region on the report design surface, click the first cell to merge. Holding the left mouse button down, drag vertically or horizontally to select adjacent cells. The selected cells are highlighted.
Right-click the selected cells and select Merge Cells. The selected cells are combined into a single cell.
Repeat steps 1 and 2 to merge other adjacent cells in a data region.