The letter, in capital letters and no punctuation, added that any harm to staff or public would be the branch's fault.
Two boxes similar to greengrocer crates had been left in the reception area, one inside the other and covered in black bags and tape.
The bomb scare caused the town centre to be cordoned off for several hours, Maidstone Crown Court heard.
Esqulant was arrested at an address in West Kingsdown, near Sevenoaks, less than four hours later.
Police searched the property and found the HMRC letter dated December 24 2015, addressed to Esqulant Consultancy Limited and for £106,162.95 (NZ$193,352.42)
They also found another letter, dated December 4, asking for outstanding VAT returns.
The court heard he had also received a text message from an accountant asking for payment of £2,706 (NZ$4928.38).
Prosecutor Jennifer Oborne said at the start of the trial: "The Crown simply state he was in serious debt and was driven to desperate measures to alleviate that debt.
"At the time he was clearly finding life extremely difficult but the methods he used to alleviate that financial burden was wholly inappropriate and caused several people an awful lot of fear and distress."
William Ryan, defending, said his client admitted planting the bomb hoax and handing over the letter, but his defence "turns" on why he did it.
"He will say he only wanted to speak to the bank manager and the reason for this was the bank was sending threatening letters and making antagonistic phone calls regarding missing mortgage payments for his family home in Harrietsham."
"He said he would have effectively had words with the bank manager and ask him how he would like getting threatening letters.
"He said he had no intention to get any money or cause loss to the bank and to that end he will rely on the fact he didn't disguise himself in an area where he was known very well in licensing of pubs in the area for a long time."
Esqulant denies blackmail, taking a VW Golf without the owner's consent and driving while disqualified.
The vehicle was spotted in the area at the time of the bomb hoax and Esqulant is alleged to have been at the wheel.
The trial continues.