First things first: let's make sure what "mora" means in Nicaraguan tax law:

"Arto. 130. Constituye mora la falta total o parcial de pago de los tributos desde el vencimiento del plazo para su cumplimiento, sin necesidad de requerimiento alguno."

OK, but then article 131 indicates that it includes late filing:

"Toda persona que presente tardíamente su declaración y/o pago de tributos y por tal motivo incurra en mora, deberá pagar el crédito correspondiente con un recargo del 5 % (cinco por ciento) por cada mes o fracción de mes de mora [...]"
Código Tributario de Nicaragua
http://www.dgi.gob.ni/documentos/Ley_562_CODIGO_TRIBUTARIO_D...

However, in your text late filing is item (iii), so they're using "mora" in (ii) to mean just not paying on time.

If you want to use IRS terms, they use "default" for when you miss a payment in an installment scheme agreed with the IRS for payment of unpaid taxes. More generally, failure to pay by the due date is referred to as "failure to pay", though they also refer to "late paying". I'd recommend "failure to pay", because after all, in theory it could be that the tax is never paid at all. Note that the failure-to-pay penalty in the US is exactly the same as the mora penalty in Nicaragua.

"1. Two penalties may apply. If you file your federal tax return late and owe tax with the return, two penalties may apply. The first is a failure-to-file penalty for late filing. The second is a failure-to-pay penalty for paying late. [...]
4. Penalty for late payment. The failure-to-pay penalty is generally 0.5 percent per month of your unpaid taxes. It applies for each month or part of a month your taxes remain unpaid and starts accruing the day after taxes are due. It can build up to as much as 25 percent of your unpaid taxes."
https://www.irs.gov/uac/what-to-know-about-late-filing-and-l...

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Note added at 1 hr (2017-04-10 08:20:18 GMT)
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Pardon me, it's not the same penalty: the penalty in Nicaragua is ten times greater! The IRS is actually pretty kind to taxpayers in some ways, though their documentation is notoriously user-unfriendly.

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Note added at 1 hr (2017-04-10 08:23:04 GMT)
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For "contravención tributaria" you could use "tax violation", which is pretty common in legal contexts in the US.

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Note added at 1 hr (2017-04-10 08:29:37 GMT)
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By the way, I'm interested to see that the IRS treats late filing more severely than late payment. My brother tells me it's the same with HMRC in the UK, and I know to my cost that it's the same in Spain; I was once fined for late filing of a VAT return, despite the fact that there was nothing to pay.

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Note added at 2 hrs (2017-04-10 09:20:00 GMT)
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That was nice of them! I can't help wondering whether the refund was a mistake, but a good result anyway. VAT inspectors are particularly fierce, and that seems to be the same everywhere, probably because there's so much VAT fraud (it's systemic in Spain).