Presidential guidance on amending claims for judicial review:
(i) The amendment of a judicial review claim form preceding the lodgement of the Acknowledgement of Service does not require the permission of the Tribunal. Such permission is required in all other instances.
(ii) In deciding whether to exercise its discretionary power to permit amendment, the Tribunal will have regard to the overriding objective, fairness, reasonableness and the public law character of the proceedings. The Tribunal will also be alert to any possible subversion or misuse of its processes.
(iii) Every application to amend should be made formally, in writing, on notice to all other parties and paying the appropriate fee which, with effect from 21 March 2016, is £255.
(iv) Where an amendment is permitted in the course of a hearing the Tribunal may, within its discretion, not require compliance with the aforementioned requirements.
(v) There is a sharp distinction between an application to amend grounds and an application to amend the Respondent’s decision under challenge: R (HM) v Secretary of State for the Home Department (JR – Scope – Evidence) IJR  UKUT 437 (IAC) applied.
Note that amendment can potentially be made at a hearing without paying the fee. It would be a brave, foolhardy or straightforwardly poor soul to do so premeditated. Personally, I’m not sure what the sharp distinction is at subparagraph (v) and I follow these things quite closely. I think it might be that the Respondent can always amend her decision but not so the Applicant his or her grounds of challenge.
The President also warns that there might be costs consequences:
Finally, judges should be alert to the possibility that, in some cases, the respondent may incur costs in consequence of an amendment being permitted. This could arise, for example, where to permit an amendment results in a hearing date being vacated and/or requires the preparation of a substantially amended pleading. Thus the price of securing an amendment may sometimes involve the payment of costs consequently incurred by the respondent. Of course, in any case where the price of permitting an amendment of an applicant’s grounds is likely to be a hearing date being vacated, fairness, reasonableness and the overriding objective may combine to defeat the application. Every case will be unavoidably fact sensitive.