Is the filing of a card compulsory?

No, the player does not necessarily have to discard a card. In the official rules it says:

„The players have the option not to discard a discardable card“

This may be appropriate for strategic reasons.

Here is an example:
On the discard pile there is a red 7. In my hand I hold a blue 7 and green 8. I know that my next player only holds a blue card in his hand, because he wished for blue before. In this case it is advisable not to discard the blue 7 and to draw a card instead.

© 2021 | UNO ™ is registered by Mattel. All Rights reserved