Льгота действует до конца месяца.

Because льгота is the subject of the sentence — it is the thing that acts / applies / remains valid.

• льгота = nominative singular
• действует = is in effect / is valid / applies

So the basic structure is:

Льгота действует = The benefit/discount is valid / applies

Льгота is a noun that usually means some kind of benefit, concession, special entitlement, discount, reduced rate, or exemption.

Depending on context, it could refer to things like:

• a discounted fare
• a social benefit
• a reduced payment
• a special privilege or exemption

So in this sentence, льгота is not just any random “advantage”; it usually refers to an official or established benefit.

Here действует means something like:

• is in effect
• is valid
• applies
• remains in force

The verb is действовать.

Russian often uses действовать for things like:

• discounts
• tickets
• offers
• laws
• rules
• documents
• visas
• prescriptions

Examples:

• Билет действует до пятницы. = The ticket is valid until Friday.
• Скидка действует неделю. = The discount is valid for a week.

So Льгота действует means the benefit is currently valid or applicable.

The dictionary form is действовать.
The ending -ть is part of the infinitive.

When you conjugate it for he/she/it or for a singular thing like льгота, you get:

• я действую
• ты действуешь
• он / она / оно действует
• мы действуем
• вы действуете
• они действуют

Since льгота is singular, the correct form is действует.

Because до requires the genitive case.

So:

• конец → конца
• месяц → месяца

That is why you get:

• до конца месяца = until the end of the month

This is a very common pattern in Russian:

• до утра = until morning
• до вечера = until evening
• до понедельника = until Monday
• до конца года = until the end of the year

Because there are really two layers here:

1. до requires the genitive:

   • до конца = until the end

2. месяца depends on конца:

   • конец месяца = the end of the month

So:

• конец месяца = end of the month
• до конца месяца = until the end of the month

This is similar to English the end of the month, where month depends on end.

Usually, in normal everyday Russian, yes — it generally means through the end of the month.

So if someone says:

Льгота действует до конца месяца

the natural interpretation is that the benefit remains valid up to the month’s end, normally including the last day.

That said, in legal or technical contexts, exact cutoff times can depend on policy wording, so context still matters.

Yes. Russian word order is flexible.

The neutral order here is:

Льгота действует до конца месяца.

But you could also say:

• До конца месяца действует льгота.
• Льгота до конца месяца действует. (less neutral, more marked)

The first version is the most straightforward and neutral.
Changing the order usually changes emphasis, not the core meaning.

For example:

• До конца месяца действует льгота.
  Emphasizes the time frame: Until the end of the month, the benefit is valid.

Because Russian has no articles like a or the.

So льгота can mean:

• a benefit
• the benefit

Which one is intended depends on context.

In a real situation, this sentence could mean either:

• The benefit is valid until the end of the month
• A discount/benefit applies until the end of the month

Russian leaves that to context instead of using articles.

Usually it describes a current valid situation: the benefit is in force now, and that continues until the end of the month.

The present tense in Russian often works this way for schedules, validity, and rules:

• Акция действует до пятницы.
• Виза действует год.
• Правило действует с января.

So even though it is present tense, it naturally covers an ongoing period of validity.

The stress is:

льгОта дЕйствует до концА мЕсяца

A rough pronunciation guide:

• льгота ≈ lyGOta
• действует ≈ DYEYST-vu-yet
• конца ≈ kan-TSA
• месяца ≈ MYE-si-tsa

A few notes:

• льг at the start of льгота can feel awkward for English speakers.
• действует contains the ей sound, like dyeyst-.
• Stress matters in Russian, so it is worth learning these forms with stress from the beginning.