Prevent Opportunity creation upon Lead Conversion

Use validation rule to prevent Opportunity creation upon Lead conversion

• For the error Condition Formula, insert the Checkbox field you just created.
• For the error message, try something like 'Do not create an Opportunity from a Lead.'
• Set to display on top of the page.

Detailed Steps:

Create the checkbox on Opportunity:

Salesforce Classic: Setup | Customize | Opportunities | Fields

1. Click New
2. Choose "Checkbox"
3. Enter a name for the field
4. Tick "Unchecked" for Default Value
5. Click Next
6. Set the profiles that can view the field
7. Click Next
8. Click Save

Create a Checkbox field on Leads, default Checked:

1. Click New
2. Choose "Checkbox"
3. Enter a name for the field
4. Tick "Checked" for Default Value
5. Click Next
6. Set the profiles that can view the field
7. Click Next
8. Click Save

Map the Lead field to the Opportunity field:

1. Scroll down to "Lead Custom Fields & Relationships" section
2. Click Map Lead Fields button
3. Click "Opportunity" tab
4. Choose the checkbox you created to map the one you have on Lead
5. Click Save

1. Click Map Lead Fields button
2. Click "Opportunity" tab
3. Choose the checkbox you created to map the one you have on Lead
4. Click Save

Create a Validation rule on Opportunities:

1. Click New
2. Enter a Rule name
3. Under Error Condition Formula, click Insert field
4. Look for the checkbox you created and select it
5. Click Insert
6. Enter "= TRUE" after the field
7. For the Error Message, use "Do not create an Opportunity from a Lead"
8. Choose your preferred "Error Location"
9. Click Save

Classic:

1. Go to Setup | Customize | Leads | Lead Settings 

2. On the Lead Conversion Settings, Check "Select "Don't create an opportunity" by Default in Convert Lead Window"
 

Lightning:

1. Click the Gear icon then go to Setup | Feature Settings | Marketing | Lead Settings

2. On the Lead Conversion Settings, Check "Select "Don't create an opportunity" by Default in Convert Lead Window"