The Latin abbreviation nb (nota bene, "note well") could be used for this purpose.
Nota bene: you must submit your completed form before midnight. Nota bene is frequently abbreviated "NB", so it would also be fine to write, "NB: you must submit your completed form before midnight.
Nota Bene
NB as in Nota Bene
The term "nota bene" translates to English as "note well." An example of a sentence using this phrase would be: We will be in the Adirondacks this weekend; nota bene it gets very chilly at night in the mountains.
NOTA bENE
observe carefully
NB.... Note well, to take notice of. It's from Latin.
The Latin and Italian phrase 'nota bene' means note well. It is commonly used in legal papers to draw attention to certain details meaning either 'pay attention' or 'take notice'.
National Basketball ornota bene ( a Latin word meaning note well )
The Latin phrase 'nota bene' (N.B.) is used in Spanish, as it is in English
1) Nota Bene (Latin: Note Well) 2) Niobium