What type of corporation? If truly an S or C there should be a sale of personal (sole prop) assets into the corporation and the corporate entity has a new and different tax ID and as such really there should be the initiation of a new company file and not just a continuation of the existing. But, in a nutshell, in my OPINION, and "free" advice you have to close out all personal equity as of 12/31/18 and then post that equity out to initial ownership in the new entity. It makes a big difference if a true corp with shares and shareholder ownership as there is no longer owner equity contribution but would be sale of stock to the new owner for the value of A/R and assets provided.
Going from Sole Prop to single member LLC is a little simpler, moving values from Owner Equity to Member Equity and since the pass through of profit or loss is identical