The pack has been designed to replicate an architect's drawing of building plans. It comes in a poster tube and contains an A2 plan detailing ten building renovations.
Among the suggestions are an outbuilding conversion, a swimming pool, a loft conversion, under-floor heating and a new garage.
Alongside each idea is the estimated cost of the work, how much it would cost the recipient to take out a loan at a standard rate and the cost of taking a loan out as part of its One Account offering.
On the back of the plan is a table that compares the cost of taking out a standard loan with a One Account loan.
The mailing attempts to be authentic with the architect's plan style of the drawing, the paper it is drawn on and the tube, which carries an address label with the words: "Revised plans enclosed."
The mailing also contains a hand-written compliment slip that explains how switching to a One Account can help save the consumer thousands of pounds.
The campaign was written by Jonathan Bradley and art directed by Wayne Pick.
The campaign has been carefully targeted so that the mailing will only go out to homeowners who have applied for planning permission to carry out serious home improvements and those who have had planning permission already approved.