Oxford documents require + -ing, require + object + to-infinitive, and passive be required + to-infinitive. The grammar changes with who or what is being required, so a bare require-to-do contrast is misleading.
ReviewedEvidence2 sourcesSectionEnglish Usage
Quick answer
Use “require doing” when the subject is the thing that needs an action, but use “require someone to do” or passive “be required to do” for an obligation on a person. Bare “require to do” is not the ordinary direct pattern.
Key details
Confusion Familygrammar-and-usage distinction
Rule Familyverb complement pattern
TermsRequire Doing, Require To Do
Further guidance
Boundary
Do not omit the required object/passive structure and assume “require to do” behaves like an ordinary direct infinitive complement.
Construction
Oxford lists “require doing something,” “require somebody/something to do something,” and “be required to do something.”
Decision
Use the -ing pattern for a thing that needs an action; use an object + to-infinitive or passive be required + to-infinitive when stating who must act.
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
Cambridge documents both admit + -ing and admit to + -ing for acknowledging something. Other passive patterns such as “be admitted to be” are separate constructions.
Both patterns are standard. “Advise waiting” recommends an action generally or in context, while “advise him to wait” names the person who is advised to perform it. A that-clause is another standard option.
When “afford” is followed directly by another verb, standard learner references use a to-infinitive: “afford to do.” An -ing form can appear elsewhere in a sentence, but it is not a like-for-like direct complement after “afford.”
“Agree to do” expresses consent to take an action. An -ing form normally follows a preposition in patterns such as “agree with doing,” which expresses approval rather than the direct promise-to-act construction.
Cambridge documents aim + to-infinitive for intention and aim at for directing effort toward an objective. Do not omit the preposition and present bare “aim doing” as equivalent to “aim to do.”
“Allow” can take an activity as its object, as in “allow smoking,” or a person/thing followed by a to-infinitive, as in “allow visitors to enter.” The patterns answer different structural questions: what is allowed versus who is allowed to do what.
