Should you need to reach me.

Commas


Use a comma when beginning with the conditional clause.
No comma is needed when using standard sentence order.

In the event (that) you need to reach me, call me. (error)
Call me in the event you need me.

In case you need to reach me, call me.(error)
Call me in case you need me.

Should you need to reach me, call me. (error)
Call me should you need me.

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