How to Define Document Type and Number Range in SAP FICO

Enter Transaction Code SPRO in SAP Command Field

In the next screen, Select 'SAP Reference IMG'

In the next screen "Display IMG'  Follow the menu path

Financial Accounting -> General Ledger Accounting -> Business Transactions -> G/L Account Posting -> Carry out and Check Document Settings ->Define Document Types

In the next screen, Press 'New Entries' Button from the Application Toolbar

For Maintaining New Document Type

In the next screen, Enter the Following

1. Enter a unique Document Type Key
2. Enter the Document Type description
3. Select a number range for the Document Type
4. In Account Type Allowed Section , select the Account type which you would like to do posting
5. Enter Appropriate Selection in the Control Data Section 

Press 'Save'  button

In the next screen , Enter the Customizing request number to create the new G/L Document Type

For Maintaining new Number Range

Press 'Number range Information' Button in the properties section

In the next screen ,

1. Enter the Company Code for which you want to maintain the number range
2. Press 'Change Interval ' Button 

In the next screen , Press 'Insert Interval'  Button

In the next screen,

1. Enter a unique number range key
2. Enter the fiscal year for which the range is defined
3. Enter the Start Number and End Number of range without overlapping other Number Ranges
4. Mark it as External if you want to insert the Document number manually during document creation
5. Press 'Insert' Button 

In the next screen , the new number range is listed