I am currently working m way through receipts and its not letting me match receipts to expenses before 31//3/21 any idea why?

It's an honor to assist you today, userclairewlane.

There are a few reasons why transactions like receipts are not being match from your existing transactions in QuickBooks Online (QBO) like expenses.

QuickBooks may not recognize a match due to the following reasons:

• The transaction is not in the books.
• The transaction is older than 180 days.
• The transaction that you've imported is a payment/ deposit of two or more open transactions in QuickBooks.
• The transaction was recorded in a different bank account.

Here are also some criteria that could prevent the program from matching. Kindly check these:

1. Verify the transaction first.
2. Make sure the QuickBooks Online transaction has not been previously matched to another transaction.

Since the expenses were older than 180 days already, you may want to add a new one.
 
You can read more of these articles about matching and managing receipts: Upload your receipts and bills to QuickBooks Online

I'm leaving you this article about matching and categorising transactions: Match and categorise the downloaded transactions.

Get back to me if you have additional queries while handling fees in QBO or any other questions. I'm always here to help, Have a great day ahead!