The guys are right, please do go back a review whether or not you actually missed the payment. You may well have made the payment or perhaps you sent the check but it was never cashed.
The comments about judges are misplaced though. Judges do act that way on residential leases. They are much more reluctant to mess around with commercial leases. The assumption is that a business lease (contract) is entered into on a more equal basis and the agreement made was made with eyes open. Not always the case, but it is the general practive to uphold leases rather than require change. You are also very unlikely to ever get in front of a judge over a 5K dispute. The legal fees will exceed that before you get to court. Most likely, your lease requires mediation or some other approach to dispute resolution in any case. Also, very likely, your lease will require the loosing party to cover the prevailing party’s expenses in the dispute.
My advice (remember, it is worth what you paid for it) is:
First, confirm whether or not the rent was paid or a check mailed etc. If the check was mailed and cashed, get documentation, if mailed but never cashed, ask for a compromise.
Second, if the rent was not paid, check your lease for several things: Clause regarding late rent and penalties, interest etc, clause regarding notice for address, dates, required time for response. Try to determine what the lease actually requires. Certainly you can ask for a compromise, but in the end, paying what the lease requires is going to be a LOT better than trying to fight it over such a small amount of money.
If the LL did not follow proper proceedure for notifying you they will need to back off on the interest cost. Very likely, the notice requirement says that they need to send the letter by certified mail. If so, the certified letter they sent was the actual notice under the lease and you have a chance to say that the interest needs to be adjusted. Bottom line CHECK THE LEASE.
On another topic, guys, I can tell you from several years of SCORE counseling activity, that MANY businesses are more than capable of missing a 4K payment and not noticing it in the cash flow. Far too many businesses simply look at total sales and the balance of available cash and not much else. This goes right along with the posts we see here all the time from pizza store owners that do not know how to figure out food costs or labor costs.