How am i able to deduct for lost rental income.

[nkulesh]

Received $300 in a 7-1/2 month period. Rent was $700 a month

[Carl]

There's no such thing as lost rental income. You can't lose that which you were never paid.

[KrisD · Accepted solution]

You never report "lost income".

You only report income and expenses.

As far as the IRS is concerned, you can't "deduct" something you never received.