One letter is missing in surname - how to solve this in document verification?

1, Is your name correct on all your certificates? Then I think there will not be any issue. They might have asked for clarification before calling for the examination and interview. It can be treated as a typographical mistake and ignored by the authorities.
2. If there is a difference in any certificates, you may have some problems. Then you may have to apply for correction through the authorities.
3, In any case, a court affidavit will serve the purpose. To be on the safe side, contact any lawyer in your area and ask him to get an affidavit and keep it with you. When you go for certificate verification you can show that affidavit and tell them that the correction process is already initiated.
4. These days if the correction is there in any of your certificates, you have to get a Gazette publication. This process starts with an affidavit, then publishing the same in two news papers and then applying for gazette publication. This process also will be known to the lawyers and you can get their help.

As mentioned above, there would not be a problem with any kind of test. Generally, It is considered a typographical error, and If you are afraid that they would reject you while document verification. So, you contact a lawyer and ask him to make an affidavit. And show it during the document verification and ensure them that the correction process has started. After that publish it the same in two local news papers and apply for gazette publication.

Whether it is one letter or more letters any change in name is to be rectified otherwise there will be mismatch during the document verification session. This is a serious matter and it has to be rectified at an earliest.
What you have to do is that make an court affidavit by taking help of some lawyer and mention all the relevant details about the mistake made in the application form. Attach copy of all the documents with the affidavit making references on each page. You will have to sign in the affidavit and it will be countersigned by the magistrate. Copies of all the supporting documents would be attached with the affidavit and would be its part only.
Now keep a copy of the affidavit as ready reference with you and take it when you go for document verification process. You have to keep the original documents also with you so that if the verification authority wants to crosscheck then it can be done easily.

It is obvious getting boredom while seeing similar posts about the spelling difference / space in name etc., found in the school/college/university certificates, it is an alert to others the essentiality of the verification of such certificates immediately on receipt of the same without neglecting and no postponement should be there for needy correction.
I have received my Hindi Certificate from New Delhi as Ms. Rama Chandran (as a small space between the name changed the gender) and on seeing the difference immediately on receipt, I sent back the same with a covering letter for correcting. Though it would not affect my career, I did the same and got it corrected.

It hardly matters that a single letter or a couple of words is missing from your surname. It will ultimately create a problem during the official verification stage and hence this anomaly needs to be resolved at the earliest so that IMA authority does not raise any objection during the documentation verification stage.
The first initiative you can take up at this stage is to apprise the concerned official of the lapse occurred from your end through a registered speed post accompanying an acknowledgment receipt in the favour of your name. You inform the authority that the same would be corrected before the final stage of documentation verification.
Meet a lawyer along with the photocopies of the essential certificates such as mark- sheets and certificates of the different examinations ( from class ten & onwards) apart from the photocopy of your application submitted to the authority. Your lawyer will help you in the process of affidavits. The affidavit countersigned by the magistrate along with your signature at the end will be of your great help to you.
You will have to post an advertisement both in a local newspaper and the leading English Newspaper highlighting that the correction in the application has been done. Preserve this cutting to be shown to the appropriate authority during the stage of document- verification.