Whenever you see the verb have in any of its forms (have, has, having, had), be sure that the verb that follows it is in the past participle form (Verb III).

We had complete* their work
They have went* to the market
*) error indication

Pada contoh pertama, verb complete seharusnya adalah kata kerja bentuk ke-3 (V-III) yaitu completed karena kata kerja tersebut setelah had.  Pada contoh ke dua, kata kerja went seharusnya kata kerja bentuk ke-3 (V-III) atau past participle yaitu gone karena muncul setelah have.

Pattern    :   verb form after have => Have + past participle