
Regular verb: head - headed - headed
Simple form | V-ing form | 
| I must head you must head she must head we must head you must head they must head  | I must be heading you must be heading she must be heading we must be heading you must be heading they must be heading  | 
Perfect | V-ing perfect | 
| I must have headed you must have headed she must have headed we must have headed you must have headed they must have headed  | I must have been heading you must have been heading she must have been heading we must have been heading you must have been heading they must have been heading  | 
Simple form | V-ing form | 
| I mustn't head you mustn't head she mustn't head we mustn't head you mustn't head they mustn't head  | I mustn't be heading you mustn't be heading she mustn't be heading we mustn't be heading you mustn't be heading they mustn't be heading  | 
Perfect | V-ing perfect | 
| I mustn't have headed you mustn't have headed she mustn't have headed we mustn't have headed you mustn't have headed they mustn't have headed  | I mustn't have been heading you mustn't have been heading she mustn't have been heading we mustn't have been heading you mustn't have been heading they mustn't have been heading  | 
Simple form | V-ing form | 
| must I head? must you head? must she head? must we head? must you head? must they head?  | must I be heading? must you be heading? must she be heading? must we be heading? must you be heading? must they be heading?  | 
Perfect | V-ing perfect | 
| must I have headed? must you have headed? must she have headed? must we have headed? must you have headed? must they have headed?  | must I have been heading? must you have been heading? must she have been heading? must we have been heading? must you have been heading? must they have been heading?  | 
Simple form | V-ing form | 
| mustn't I head? mustn't you head? mustn't she head? mustn't we head? mustn't you head? mustn't they head?  | mustn't I be heading? mustn't you be heading? mustn't she be heading? mustn't we be heading? mustn't you be heading? mustn't they be heading?  | 
Perfect | V-ing perfect | 
| mustn't I have headed? mustn't you have headed? mustn't she have headed? mustn't we have headed? mustn't you have headed? mustn't they have headed?  | mustn't I have been heading? mustn't you have been heading? mustn't she have been heading? mustn't we have been heading? mustn't you have been heading? mustn't they have been heading?  |