Trying to import data from quickbook desktop 2015 to online but not working because my old data is huge and quickbook online shows it can import 2MB of data

How big is your file size? Open it on trial license of Pro 2020.

https://quickbooks.intuit.com/learn-support/en-us/new-subscriptions/download-a-trial-of-quickbooks-d...

Consider to condense it prior to migrate to QBO. As last resort, consider purchasing a 3rd party condense service to compress it. 

Always work from the most recent version - that is major reason for trial versions (note they cannot be registered - attempts to register will actually lock the program). The condense utility in QB2020 is far superior to that in QB2015.

I highly recommend backing up your full-sized file prior to condensing since the act of condensing combines all condensed data (before a set date) into a single journal entry.

Hello phinaspharma,

Let me help you figure out what's going on here, The problem you're encountering is happening because QuickBooks Online is a cloud storage service, while QuickBooks Desktop is a Hardwired system service. This essentially means that there is a limit to what you can and can't have uploaded onto your online account. It's that way so we can keep the program running quick and smooth for everyone. If your file is too big to upload to QuickBooks Online Id recommend taking your Desktop file and either using the Condense data utility tool or Exporting from the old company file into a new data file. Use these steps below:

Condense Data:
1. Go to File Select Utilities and then select Condense Data.
2. Select the first option 
3. Select Next and the notice Working on your file now Will appear. When complete, a window opens advising you of the total reduction in your file size as well as the location of the backup prior to the file optimization. 

Export Lists:
1. Go to File menu, then select Utilities
2. select Export, the Lists to IIF Files
3. Select the list you want to export, then select OK
4. Browse the location where you want to save your file and select Save.

Import the list:
1. Sign in to your company file as Administrator
2. Switch to single user mode
3. Go to File menu, then select Utilities
4. Select Import, then IIF Files
5. Import the Chart of Accounts.
6. After successfully importing the Chart of Accounts, import the other list following this order.
Import the lists that do not contain information from other lists.
-Customer Type List
-Vendor Type List
-Class List
-Job Type List
-Payment Terms List
-Payment Methods List
-Shipping Methods List
-Customer Message List
-To Do Notes

Import the following lists one by one in this order:
-Vendor
-Employee
-Other Names
-Sales Rep
-Item
-Price Level
-Customer
-Budgets

 I attached articles to the Steps above that breakdown each one in further detail. Let me know if you need anything else, Hope this helps!