In exceptional circumstances, if there are reasons why it wasn’t possible to table an amendment to a substantive motion before the deadline—if, say, information that made the amendment desirable came to light only on the day of the debate—you can submit a manuscript amendment on the day.
To do this, speak to Table Office, or to the clerks sitting at the table in front of the Speaker in the Chamber, who will advise you on whether your manuscript amendment is in order. If it is, and the Speaker selects it, the Speaker will call you to move it and give a speech in support of it.
Manuscript amendments are not usually selected.