IPA: /ˈdjuːli/
KK: /ˈduːli/
In a proper or expected way, often at the right time or in the right manner.
The documents were duly signed by all parties involved.
Duly → It originates from the Old English 'dūlīc', meaning 'in accordance with'. The word 'duly' means in a proper or appropriate manner, as expected or required.
Think of doing something 'in accordance with' what is expected — that's why 'duly' means to do something properly.