Post Rebus #799

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Do you need a little help? Click to reveal a clue to the above Rebus.
Here is a clue to help decipher the hidden meaning. Said to reassure a payment is on the way.
Do you think you have got it? Click to view the answer.
The word “Post” [Mail] is checkered, to give the answer: Cheque/Check Is In The Post/Mail .