Format of letter requesting client for extension of the due date of bid submission
There is a prescheduled time frame to submit your bid for every NIT. If you watch a notice inviting tender (NIT) lately and feel that there is very less time to participate, you can write a letter to the customer requesting to extend the due time of bid submission. Here is a typical example of such letter.
When you are preparing a techno-commercial offer against a notice inviting tender, you have to assess the entire scope of supply and work to get an exact estimation and pricing. Accordingly, sometimes you may need a few more times than the specified time schedule to submit your offer mentioned in the NIT. In such case, you may send a requesting letter which is one of the important types of business letter, to the notice inviter to extend the time schedule for bid submission which is mentioned in the NIT and customers often consider such request if they feel its reality. However, a typical format of the letter on this subject is being given below for your reference. Also, note that you need the letterhead of your organization to write such a letter and to get a positive result. That's why the sender's address is skipped here.
[Date]
To
[Name of Purchaser (organization)],
[Address of the organization]
Kind Attn. : [Name of contact person], [his designation](you have to write the name of the contact person and his designation which have been mentioned in the NIT for communication. If there is none to communicate, write the name and designation to whom your offer will be addressed as written in NIT. Write Mr. for male and Ms. For female before the name of the contact person)
Ref. – [NIT no.] dated [Date of NIT]
Sub. – Request for the extension of the due date of bid submission by at least 15 days(Make the subject line in bold to highlight the matter)
Dear Sir,(Salutation will depend on the gender of the person who is being addressed in the attention line. Use Madam Instead of Sir if the person is a lady)
We would like to inform you that our organization has been serving [Name of the work] to various organization since last [time period of your company's business]. Accordingly, we are very much interested to participate in your above NIT. But kindly note that to prepare an exact estimation in line with your requirement and to make our best competitive offer we need a few more times and accordingly, you are requested to extend the due date of the bid submission by at least 15 days.(Note that name of work will be same as asked in the NIT or what your organization serves. Note that both will be the same because only in that case your organization will be interested to participate in that NIT)
We look forward to your kind consideration and assure you the best of our services every time.
Thanking you,
Yours truly,
[Your signature]
[Your name],
[Your designation]

Follow
Good idea for the nature of letter you disclosed. But in practical every company issue NIT for getting work done by the contractors with in a time schedule.
And regarding completion of formalities i,e, NIT to TCR and award of works order kill a vital time.
Other bidders who have already offer their BID with in schedule time will not permit the company to extend the period further and in such cases the company did not do that legally.
In exceptional cases if their are no offer or single offer and the management has not sufficient delegation of power for approving the works order based on single offer/tender basis , in that case the time limit may be extended.
However thanks for such a quality resources.