Is the grammar correct kindly return after use?

The grammar in the phrase "kindly return after use" is correct. However, it's a bit formal and could be improved for everyday use. Here are some alternatives:

More casual:

* Please return after use.

* Return after use, please.

* Don't forget to return after use.

More specific:

* Please return this [item] after use.

* Kindly return the [item] after you are finished.

The best choice depends on the context and your intended tone.