I could tiptoe you could tiptoe he could tiptoe we could tiptoe you could tiptoe they could tiptoe
V-ing form
I could be tiptoing you could be tiptoing he could be tiptoing we could be tiptoing you could be tiptoing they could be tiptoing
Perfect
I could have tiptoed you could have tiptoed he could have tiptoed we could have tiptoed you could have tiptoed they could have tiptoed
V-ing perfect
I could have been tiptoing you could have been tiptoing he could have been tiptoing we could have been tiptoing you could have been tiptoing they could have been tiptoing
Negation
Simple form
I couldn't tiptoe you couldn't tiptoe he couldn't tiptoe we couldn't tiptoe you couldn't tiptoe they couldn't tiptoe
V-ing form
I couldn't be tiptoing you couldn't be tiptoing he couldn't be tiptoing we couldn't be tiptoing you couldn't be tiptoing they couldn't be tiptoing
Perfect
I couldn't have tiptoed you couldn't have tiptoed he couldn't have tiptoed we couldn't have tiptoed you couldn't have tiptoed they couldn't have tiptoed
V-ing perfect
I couldn't have been tiptoing you couldn't have been tiptoing he couldn't have been tiptoing we couldn't have been tiptoing you couldn't have been tiptoing they couldn't have been tiptoing
Interrogative form
Simple form
could I tiptoe? could you tiptoe? could he tiptoe? could we tiptoe? could you tiptoe? could they tiptoe?
V-ing form
could I be tiptoing? could you be tiptoing? could he be tiptoing? could we be tiptoing? could you be tiptoing? could they be tiptoing?
Perfect
could I have tiptoed? could you have tiptoed? could he have tiptoed? could we have tiptoed? could you have tiptoed? could they have tiptoed?
V-ing perfect
could I have been tiptoing? could you have been tiptoing? could he have been tiptoing? could we have been tiptoing? could you have been tiptoing? could they have been tiptoing?
Interro-negative form
Simple form
couldn't I tiptoe? couldn't you tiptoe? couldn't he tiptoe? couldn't we tiptoe? couldn't you tiptoe? couldn't they tiptoe?
V-ing form
couldn't I be tiptoing? couldn't you be tiptoing? couldn't he be tiptoing? couldn't we be tiptoing? couldn't you be tiptoing? couldn't they be tiptoing?
Perfect
couldn't I have tiptoed? couldn't you have tiptoed? couldn't he have tiptoed? couldn't we have tiptoed? couldn't you have tiptoed? couldn't they have tiptoed?
V-ing perfect
couldn't I have been tiptoing? couldn't you have been tiptoing? couldn't he have been tiptoing? couldn't we have been tiptoing? couldn't you have been tiptoing? couldn't they have been tiptoing?