---
title: "Replacing a Rating Table"
canonical: "https://docs.rubiconwater.com/space/DC/2048721248/Replacing%20a%20Rating%20Table"
format: markdown
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> Macro (toc)

Replace a rating table when the original rating table was correct, but you want to start using an updated rating table. You might do this for example, if conditions have changed and the old rating table is no longer applicable.

> ℹ️ **Note**
> ℹ️ 
> ℹ️ If you replace a rating table, the old rating table is NOT retired. It remains valid for data collected while it was active. If you recalculate your data, the derived data is calculated using the rating table that was active when the source data was collected.
> ℹ️ 
> ℹ️ If you want to change the rating table used to calculate historical data, you should [retire](https://rubiconwater.atlassian.net/wiki/spaces/DCNC/pages/2048721228) the original rating table instead of replacing it.

To replace a rating table:

1. In the Rating Tables module, select the rating table that you want to replace.
2. Click **Replace Rating**. At the prompt, click *Yes* to confirm that you want to proceed.The application creates a copy of the old rating table. You can edit this copy to create your new rating table.
3. Enter a **Start Date** for the new rating table and make any necessary changes to the equation or data points. For example:
  - On the Details tab, click **Edit** to change the rating equation, rating points, or interpolation method.
  - On the Points tab, **Insert**, **Modify**, or **Delete** data points, or **Import** new points from a spreadsheet.
4. Click **Recalculate Tag Events** to apply the changes to your historical data.
  - Specify the date range for the recalculation and click **Find**. The application finds any relevant source data and recalculates the derived data using the new rating table.
  - Check the recalculated data.
5. If you are happy with the recalculation, click **Save** to save your changes and update the data.

> ℹ️ **Caution**
> ℹ️ 
> ℹ️ You may see a prompt asking you to confirm that you want to **retire** the old rating table. This is misleading. The old rating table will NOT be retired, it will simply be replaced. Click **OK** to proceed.

The application sets the **End Date** of the old rating table to the **Start Date** of the new table.

The old rating table remains valid and will be used to calculate the derived value for any source values that fall within its start and end dates.

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