Náhradní lhůta začne po platebním výměru.

Because po here means after, and in this meaning it takes the locative case in Czech.

So:

• po = after
• platební výměr = the payment assessment / payment order
• po platebním výměru = after the payment assessment

The forms are locative singular:

• platební → platebním
• výměr → výměru

This is a very common thing to learn: some prepositions require a specific case, and po often requires the locative.

Lhůta means a time limit, deadline, or prescribed period.

It is a feminine noun:

• nominative singular: lhůta
• genitive singular: lhůty

In legal or administrative Czech, lhůta is very common. It usually refers not just to time in general, but to an official period within which something must happen.

Náhradní means something like substitute, alternative, replacement, or additional/remedial, depending on context.

In the phrase náhradní lhůta, it usually means an additional period allowed later, often because the original period was missed or another period is being granted instead.

Grammatically, náhradní is an adjective agreeing with lhůta:

• lhůta is feminine singular nominative
• so the adjective is also feminine singular nominative: náhradní

Začne is the future form of the perfective verb začít.

• začít = to begin / to start
• začne = will begin

Czech often uses a perfective verb when talking about a single completed event in the future. Here, the sentence refers to the moment when the period starts, so začne is natural.

Compare:

• lhůta začne = the period will begin
• lhůta začíná = the period begins / is beginning (more present-time or habitual in feel)

So začne fits a legal statement about when something will start.

Czech does not have articles like English a/an and the.

So a Czech sentence often leaves definiteness to context. In this sentence, náhradní lhůta and platební výměr can be understood as definite from the situation, even though there is no separate word meaning the.

That is normal in Czech:

• Náhradní lhůta can mean the substitute period or simply a substitute period
• the exact sense depends on context

Výměr is a masculine inanimate noun.

Its dictionary form is výměr. After po, it must go into the locative singular, which here is výměru.

So:

• nominative: výměr
• locative: výměru

This is one reason Czech can feel tricky to English speakers: the ending changes depending on the role of the word in the sentence and the preposition used with it.

It is very much a legal/administrative term.

Platební výměr is an official document or decision, especially in tax or administrative contexts. Depending on the exact system and context, English translations may vary, for example:

• payment assessment
• payment order
• assessment notice

So it is better to think of platební výměr as a set phrase, not just payment + measurement or something literal like that.

Yes. Czech word order is more flexible than English word order.

For example, these are both possible:

• Náhradní lhůta začne po platebním výměru.
• Po platebním výměru začne náhradní lhůta.

Both mean essentially the same thing. The difference is mainly about emphasis or information structure.

• Starting with Náhradní lhůta puts focus on the period itself.
• Starting with Po platebním výměru foregrounds the time relationship: after the payment assessment.

In formal legal style, both kinds of ordering are possible.

A rough pronunciation guide is:

Náhradní lhůta začne po platebním výměru
NAA-hrahd-nee LHOO-tah ZAHCH-neh po PLAH-tehb-neem VEE-mnye-roo

A few pronunciation points:

• á is a long vowel
• lh in lhůta is pronounced; the l is not silent
• ů sounds like a long oo
• č in začne sounds like ch in check
• ě in výměru affects the preceding consonant and is not pronounced exactly like plain e

Also, Czech stress normally falls on the first syllable of each word.

Very often, yes, but it is useful to learn it by meaning and usage rather than as an absolute rule detached from context.

With the meaning after, po takes the locative:

• po obědě = after lunch
• po práci = after work
• po platebním výměru = after the payment assessment

So for this sentence, the important thing to remember is:

• po
  • locative = after

Sometimes yes, but you should be careful.

In some contexts, náhradní lhůta may function similarly to what English calls a grace period, additional period, or extended deadline. But the best translation depends on the legal context.

A safe learner-level understanding is:

• náhradní lhůta = an additional or substitute period allowed for something

If you are translating legal texts, it is better to check the exact technical meaning in that area of law rather than assume one English equivalent always fits.