How do you say not now but later in sign language?

There isn't a single sign for "not now but later" in American Sign Language (ASL). It's usually expressed using a combination of signs and facial expressions. Here's a common way to sign it:

1. Sign "NOW": This is the sign for "now," typically made by touching your forehead with your index finger.

2. Shake your head "NO": This indicates negation, meaning "not now."

3. Sign "LATER": This sign involves making a "L" shape with your hand and moving it forward in a sweeping motion.

4. Facial expression: Combine the signs with a slight smile or a nod, indicating that you are willing to do it later.

You can also add context to your signing by using other signs. For example, you could sign "LATER" followed by "TIME" or "DAY" to specify a more definite timeframe.

Remember that sign language is a visual language and relies heavily on facial expressions and body language. Practice signing with a native ASL speaker or through ASL resources to learn the proper nuance and context.