To get monthly report of Income and expenditure, You have to go to Income & expense A/c. This report is available at
Gateway of Tally > Income & Expense Account.
After selecting this option from the menu, the Income & Expense A/c will open.
Click on Period button provided at the right hand side of the report. You can use shortcut key F2.
Enter the month starting date and month end date. Then press enter key. This will brings you the desired report.
By default tally comes with Profit & Loss account instead oof Income & Expense A/c, If you want it to be changed as Income & Expense A/c do the following
Go to F11 Features > Accounting Features >Accounting Features
Activate option 'Use Income and expense A/c instead of Profit & loss account.
The option will change to Income & Expense Account