'Do' and 'does' are both equally forms in the existing indefinite tense of the verb 'to complete.' Which just one you can use will generally rely upon the sentence's topic. Their utilization is sort of similar, aside from one occasion where You need to use 'do' rather than 'does.' https://financefeeds.com/cardano-and-xrp-prices-set-for-major-crash-investors-take-shelter-in-payfi-rival-up-over-400/