Basically, you will report that home office as "closed" on the date you moved out of the property at the latest. Then if you purchased a new home you would open a completely new home office in the new digs. The open date for the new home office can not be the same as or overlap the close date of the old office, and it can't be before the day you moved in. In the end, you would be reporting two home offices on the 2018 tax return. The old one you closed, and the new one you opened. So long as the close/open dates are not the same date and don't overlap, it's no big deal.
